https://vimeo.com/307573320?ref=em-share [vimeo.com]
And
https://vimeo.com/321053835 [vimeo.com]
Found 340 posts.
Search results Show results as topic list.
Houdini Indie and Apprentice » Info help with modeling a flower.
- Island
- 340 posts
- Offline
Houdini Indie and Apprentice » Info help with modeling a flower.
- Island
- 340 posts
- Offline
It is true that subdivision gives more resolution, but it essentially cuts edges in half rather than putting sharpness just where you want them (near the edges). If you omit the edge loops, the edges will look smoother but you will lose the points in the petals.
It is a little annoying that there is not more control over edge loops in Houdini. In most programs, 90% of the subdivision polymodeling is moving points, inner and regular extrudes, and edge loops. Edgeloops are important if you want to subdivide your model and keep some sharpness of the edges (like pointed petal ends). As an example, if you start with a box and add a subdivide node, it will change the box into somewhat of a sphere. If you added two edge loops near the sides in the front, top, and right viewports, a subdivide would give you a box but with a little roundedness of the edges. Usually that is what I am going for. You could do that with a bevel, but generally I try not to add bevels until the model is mostly completed, as subdivisions, bridging, etc. can be harder after a bevel.
In Houdini, I usually add an edge loop by pushing the “C” key in the viewport (not the network view) and going up and to the right to select “edgeloop”. That actually adds a polysplit, but it is a bit easier to select the edge you want to split by doing it in the viewport rather than the network view. The polysplit node is a bit cryptic, as it gives a designation of the edge and a percentage along the edge, but in a not very helpful way. The polysplit can add multiple edge loops, but unlike other programs (like Modo), you can't add just two edge loops at a 5% and 95% position simultaneously. That is why I find it annoying, but in the end, it works.
For your purposes, do what looks best. The edge loops are not necessary. You will have to add enough subdivisions to sculpt, but so long as you start with quads and limit spiders (which is easy with the topobuild node), it should be fine. If you want to change the topobuild, make sure you select the “show handle” tool, not the select tool. If the leaf shape were more complicated, I would probably have modeled just half a leaf and added a mirror node.
Sculpting does not generally cause bad topology, as it doesn't add or subtract polygons, edges, or points. It just moves them around (unless you are talking about voxel sculpting or dynamesh). BTW, I am not an expert in Houdini, and the example I gave makes little use of procedural modeling (but you could alter the mountain nodes if you wanted to scatter these flowers over a hill). People with more experience could probably give you a more complicated procedural flower, and you could learn a lot from them. The materials were deliberately very simple in the example, but materials themself can add color gradients without UVs.
It is a little annoying that there is not more control over edge loops in Houdini. In most programs, 90% of the subdivision polymodeling is moving points, inner and regular extrudes, and edge loops. Edgeloops are important if you want to subdivide your model and keep some sharpness of the edges (like pointed petal ends). As an example, if you start with a box and add a subdivide node, it will change the box into somewhat of a sphere. If you added two edge loops near the sides in the front, top, and right viewports, a subdivide would give you a box but with a little roundedness of the edges. Usually that is what I am going for. You could do that with a bevel, but generally I try not to add bevels until the model is mostly completed, as subdivisions, bridging, etc. can be harder after a bevel.
In Houdini, I usually add an edge loop by pushing the “C” key in the viewport (not the network view) and going up and to the right to select “edgeloop”. That actually adds a polysplit, but it is a bit easier to select the edge you want to split by doing it in the viewport rather than the network view. The polysplit node is a bit cryptic, as it gives a designation of the edge and a percentage along the edge, but in a not very helpful way. The polysplit can add multiple edge loops, but unlike other programs (like Modo), you can't add just two edge loops at a 5% and 95% position simultaneously. That is why I find it annoying, but in the end, it works.
For your purposes, do what looks best. The edge loops are not necessary. You will have to add enough subdivisions to sculpt, but so long as you start with quads and limit spiders (which is easy with the topobuild node), it should be fine. If you want to change the topobuild, make sure you select the “show handle” tool, not the select tool. If the leaf shape were more complicated, I would probably have modeled just half a leaf and added a mirror node.
Sculpting does not generally cause bad topology, as it doesn't add or subtract polygons, edges, or points. It just moves them around (unless you are talking about voxel sculpting or dynamesh). BTW, I am not an expert in Houdini, and the example I gave makes little use of procedural modeling (but you could alter the mountain nodes if you wanted to scatter these flowers over a hill). People with more experience could probably give you a more complicated procedural flower, and you could learn a lot from them. The materials were deliberately very simple in the example, but materials themself can add color gradients without UVs.
Edited by Island - Aug. 3, 2020 17:27:14
Houdini Indie and Apprentice » Info help with modeling a flower.
- Island
- 340 posts
- Offline
I should have mentioned, just before the polyextrude node in the petals network, you could add a sculpt node and sculpt your petals. Alternatively, you could right click the node before the polyextrude and select “save” and name the file “petals.obj”. You could import that in Blender and sculpt there and export as an obj file. Then in Houdini, you could replace everything above the polyextrude node with a file node, and select your Blender exported obj file.
The steps for modeling this are almost the same as I would do in Modo, Maya, C4D, or Blender or even zbrush. What is different in Houdini is that not only can you go back and alter a node like the polyextrude, you can also replace nodes with a file node as discussed above. That makes nodes much better than a history state or modifier stack. If you were in other programs, you would have to do a lot more remodeling.
The steps for modeling this are almost the same as I would do in Modo, Maya, C4D, or Blender or even zbrush. What is different in Houdini is that not only can you go back and alter a node like the polyextrude, you can also replace nodes with a file node as discussed above. That makes nodes much better than a history state or modifier stack. If you were in other programs, you would have to do a lot more remodeling.
Edited by Island - Aug. 3, 2020 17:23:09
Houdini Indie and Apprentice » Info help with modeling a flower.
- Island
- 340 posts
- Offline
In Houdini there are dozens of ways of doing this sort of model. One could start with some primitive and add an edit node. One could start with a line and programmatically or manually adjust this and then do a sweep. The list goes on. But, depending on complexity desired, I would start with a topobuild node within a geo, and make the basic shape of a petal. Attached is a typical quick model. UV mapping would also be very easy, but I just added some colors to show that this can be done without UV's. If you add a couple mountain nodes, your pedal shape will get more interesting (see render image).
Edited by Island - Aug. 3, 2020 16:54:15
Houdini Indie and Apprentice » Default Project Path
- Island
- 340 posts
- Offline
I'm not sure, but you might be able to change that in the Houdini.env file. That can be a bit hard to find, as it is in the hidden directory “Library” under your username on a Mac.
Houdini Indie and Apprentice » For Loop Troubleshooting
- Island
- 340 posts
- Offline
I notice you used aanoise. The default output range is -0.5 to 0.5. Don't you want a fit node before the ramp in the attributevop? Also, is there a reason you are using a color ramp rather than just a spline ramp, since you are using the Cd to remove points; or is it because you want the greyscale overlay as well? You also specify Cd.x, and I assume that must be accepting that and using Cd.r instead. Do you want different cutaways with each translation or just a subtraction from the previous cutaway? I modified your file slightly by adding a new attribute off aanoise with bind export and a fit and changed the ramp a bit. This shows that your code is indeed progressively cutting away as it scales outwards.
Edited by Island - July 27, 2020 21:17:06
Houdini Lounge » Had anyone saw the C4D node-based demo?
- Island
- 340 posts
- Offline
It is great to see nodes coming to C4D. But xpresso is still tedious to perform basic functions (you often need to use multiple nodes for just one simple expression), there are no attributes, no efficient coding language, no fluids or fire or smoke. Fixing dynamics issues is hard, since the programmers hide everything under the hood. Good rendering often requires a third party rendering engine. Even particles are yet another plugin. UV tools are still bad. Rigging is slow and buggy. Even destructive modeling is minimally better than Houdini and procedural modeling requires changing to editable mode to do even simple models. It's major claim to fame is easy to learn, logical interface, very stable, and easy to create canned motion graphics if you don't want to do anything too complicated. I don't think sidefx needs to worry.
Edited by Island - July 28, 2020 00:34:46
Houdini Indie and Apprentice » For Loop Troubleshooting
- Island
- 340 posts
- Offline
It seems to be working properly. The inner cutouts don't change with each iteration. Each iteration is transforming and you can look at the geometry node to see that the Cd.r, Cd.g, and Cd.b are increasing each time and thus cutting out points. What are you wanting it to do?
Edited by Island - July 27, 2020 12:56:50
Houdini Indie and Apprentice » Why is not this working? (UV Flatten/Seams)
- Island
- 340 posts
- Offline
Although I wouldn't do it this way, here is a UV map of a modification of your flower that still has bad edge loops. It illustrates how to map such a mesh without overlap, but the relaxation may not be ideal. One selects the polygons in the front facing areas with the eye icon turned on and creates a poly selection. Then one promotes that to an edge selection (to avoid tediously selecting the boundary). Then one uses UVflatten but adds pins to fix the overlaps. You probably know, but you can right click the terminal node and use “save” and export an obj file for use back in Blender. The downside to adding several pins is that even with UV distortion map showing, it is a bit trial and error where the pins should be moved. SideFX: consider adding a relaxUV node.
Edited by Island - July 26, 2020 17:50:05
Houdini Indie and Apprentice » Why is not this working? (UV Flatten/Seams)
- Island
- 340 posts
- Offline
Just to be clear, I am not recommending going out and buying a lot of additional programs. Programs like Quadremesher, Zbrush, Modo, and RizomUV are very useful in their own right, but also allow one to fix things after they got messed up. Clearly, it is best to not mess up the topology in the first place, and that is what I am recommending.
Regarding fixing an existing model:
Both Houdini and Blender have sculpting tools, but Blender is much better for this. They are best thought of as ways of soft selecting and moving existing polygons, preferably on a relatively low density mesh. Neither is particularly useful for intermediate or advanced sculpting, though. The reason for that is that if one moves points/vertices far enough, there is not enough geometry in those areas to get any smooth additional sculpting. One has to add subdivisions and that just causes too many polygons in areas that don't need them in order to get a reasonable number of polygons on the stretched out areas. The solution in a dedicated sculpting program is to either automatically remesh periodically as one sculpts, or to use voxel sculpting that does not depend on polygons. In addition, detailed sculpting requires such a high number of polygons that the resulting mesh is almost impossible to adequately UV map or rig, though there are some workarounds that programs like Zbrush do to lessen that flaw. In reality, one converts the high polygon mesh to a displacement map to map onto a much lower polygon mesh, that is easier to UV map and rig.
Similarly, both Houdini and Blender have UV tools, though Houdini is better much better than Blender for this. Neither is a match for a dedicated UV mapping program like RizomUV or even Modo. Dedicated UV mapping programs have the ability to break apart a model and hide areas one is not working with (the visibility node in Houdini will not work, as the polygons are still evaluated in the UV unwrap, unlike other programs) and then use various relaxing and packing algorithms to fix overlaps and distortions. They can group islands and stack similarly shaped islands. The edge selection and polygons selection tools are a lot more sophisticated than Houdini or Blender. You can do a lot of this in Houdini, but it is kind of like using soft selection moves when you want to sculpt. It can be painful if the model is complicated and the UV flatten itself needs much tweaking.
But back to your original model. You have the artistic capability and the shapes look good. In Blender, you used the solidify and subdivide modifiers. The equivalent in Houdini would be the polyextrude and subdivide nodes. Everything was fine until these got applied, and then the model itself became a lot more complicated. Sculpting itself can sometimes generate bad topology. But most likely the triangles were an export problem from Blender into Houdini. You probably tried to do some sort of remesh in Blender, which is why part of your obj model has quads and the other part, triangles. You can check in Blender with a wireframe overlay or just in edit mode, at what point things got changed into triangles. But you don't want to do that. Triangles are fine internally for rendering and even 3D printing, but they are a mess for edge loops and selecting regions (which you want to do for UV mapping). The actual number of polygons is not really the issue, as you can subdivide a 10x10x10 cube six times and keep good topology but have a million polygons. You still have good edge loops and regions can be easily defined. But if you get a mess of triangles, defining a cutting edge will be a nightmare with even several hundred polygons.
The best way I know to think of UV mapping is think of planar mapping of different regions. Any curved surface will stretch the parts with a planar map in the middle and pinch the areas at the edges (think of a map of the world and the elongation but pinching of Antarctica). But planar maps work great for satellite maps of a city, because the distortions on a small scale are not significant. So if you make a million little planar maps of parts of the whole world, everything is great, except that anything going across a seam (from one little map to the next) is a problem. So one fuses some of these little planar maps together and lives with some distortion. The final number of maps is basically the number of seams. You try to hide the seams in areas that the camera doesn't see directly, if possible. Again, there are ways to avoid dealing with any of this, like creating one big stretched out map with many distorted areas, such as one might get in Zbrush. Or one could use PTEX painting in Mari. But for mere mortals, one should best learn how to create reasonable seams and relax the projections.
If you look at the image below for a simple UVflatten of a sphere, it is very similar to planar projections after just breaking up the polygon mesh into parts. The attached hip file shows the differences between a simple UVflatten and dividing up the model and UV projecting in the attached hip file. Basically the UVflattening does some relaxation of the islands that get distorted by the planar projection. But otherwise they are similar. (In a dedicated UV program, one could convert the planar projection to the UVflatten by a simple optimize or relaxation). In Houdini, you could fix this particular model with the UVflatten node by just using the align tool.
I should mention that UVflatten allows some manipulation of the mapping, by adding pins and straightening seams. But this is quite time consuming and inefficient compared to standard relaxing or reshaping algorithms.
Regarding fixing an existing model:
Both Houdini and Blender have sculpting tools, but Blender is much better for this. They are best thought of as ways of soft selecting and moving existing polygons, preferably on a relatively low density mesh. Neither is particularly useful for intermediate or advanced sculpting, though. The reason for that is that if one moves points/vertices far enough, there is not enough geometry in those areas to get any smooth additional sculpting. One has to add subdivisions and that just causes too many polygons in areas that don't need them in order to get a reasonable number of polygons on the stretched out areas. The solution in a dedicated sculpting program is to either automatically remesh periodically as one sculpts, or to use voxel sculpting that does not depend on polygons. In addition, detailed sculpting requires such a high number of polygons that the resulting mesh is almost impossible to adequately UV map or rig, though there are some workarounds that programs like Zbrush do to lessen that flaw. In reality, one converts the high polygon mesh to a displacement map to map onto a much lower polygon mesh, that is easier to UV map and rig.
Similarly, both Houdini and Blender have UV tools, though Houdini is better much better than Blender for this. Neither is a match for a dedicated UV mapping program like RizomUV or even Modo. Dedicated UV mapping programs have the ability to break apart a model and hide areas one is not working with (the visibility node in Houdini will not work, as the polygons are still evaluated in the UV unwrap, unlike other programs) and then use various relaxing and packing algorithms to fix overlaps and distortions. They can group islands and stack similarly shaped islands. The edge selection and polygons selection tools are a lot more sophisticated than Houdini or Blender. You can do a lot of this in Houdini, but it is kind of like using soft selection moves when you want to sculpt. It can be painful if the model is complicated and the UV flatten itself needs much tweaking.
But back to your original model. You have the artistic capability and the shapes look good. In Blender, you used the solidify and subdivide modifiers. The equivalent in Houdini would be the polyextrude and subdivide nodes. Everything was fine until these got applied, and then the model itself became a lot more complicated. Sculpting itself can sometimes generate bad topology. But most likely the triangles were an export problem from Blender into Houdini. You probably tried to do some sort of remesh in Blender, which is why part of your obj model has quads and the other part, triangles. You can check in Blender with a wireframe overlay or just in edit mode, at what point things got changed into triangles. But you don't want to do that. Triangles are fine internally for rendering and even 3D printing, but they are a mess for edge loops and selecting regions (which you want to do for UV mapping). The actual number of polygons is not really the issue, as you can subdivide a 10x10x10 cube six times and keep good topology but have a million polygons. You still have good edge loops and regions can be easily defined. But if you get a mess of triangles, defining a cutting edge will be a nightmare with even several hundred polygons.
The best way I know to think of UV mapping is think of planar mapping of different regions. Any curved surface will stretch the parts with a planar map in the middle and pinch the areas at the edges (think of a map of the world and the elongation but pinching of Antarctica). But planar maps work great for satellite maps of a city, because the distortions on a small scale are not significant. So if you make a million little planar maps of parts of the whole world, everything is great, except that anything going across a seam (from one little map to the next) is a problem. So one fuses some of these little planar maps together and lives with some distortion. The final number of maps is basically the number of seams. You try to hide the seams in areas that the camera doesn't see directly, if possible. Again, there are ways to avoid dealing with any of this, like creating one big stretched out map with many distorted areas, such as one might get in Zbrush. Or one could use PTEX painting in Mari. But for mere mortals, one should best learn how to create reasonable seams and relax the projections.
If you look at the image below for a simple UVflatten of a sphere, it is very similar to planar projections after just breaking up the polygon mesh into parts. The attached hip file shows the differences between a simple UVflatten and dividing up the model and UV projecting in the attached hip file. Basically the UVflattening does some relaxation of the islands that get distorted by the planar projection. But otherwise they are similar. (In a dedicated UV program, one could convert the planar projection to the UVflatten by a simple optimize or relaxation). In Houdini, you could fix this particular model with the UVflatten node by just using the align tool.
I should mention that UVflatten allows some manipulation of the mapping, by adding pins and straightening seams. But this is quite time consuming and inefficient compared to standard relaxing or reshaping algorithms.
Edited by Island - July 28, 2020 12:46:19
Houdini Indie and Apprentice » Why is not this working? (UV Flatten/Seams)
- Island
- 340 posts
- Offline
I generally do manual retopology if I plan to rig the model or want to get the best polycount, but that remesh was a one click in Zbrush (which would be similar to quadremesher plugin for Blender). The topology in the original is not good as the object has an unnecessarily large number of polygons, which creates problems such as you already discovered with UVflatten. Your model actual has two parts with disconnected polygons and one part is all quads and the other all triangles. The biggest part is all triangles. That creates havoc with selecting edge loops, and I don't know how much time it took to select the boundary, but it was likely tedious. Even autoretopology can create problems with spiral edge loops, but it isn't that difficult to fix this afterwards.
Regarding mesh overlaps, you could prevent this entirely in one of two ways. Since you have a seam, you can add a blast or delete node and remove all polys on one side of the loop. Then create another blast node and delete the polys on the other side of the loop. Perform UV mapping separately on each part and then merge them together and pack the UVs.
The second way would be to use a UVedit node and either move the vertices or just break off the areas where there is overlap (the equivalent of adding an extra seam). (see attachment, done in Modo, but could have been done in Houdini with UVedit)
Coloring the mesh can actually be done in Houdini/Mantra without UVs at all, since you can ramp the point position or point normal to a color. But if you are doing proper UV's, it depends on how you plan to color your model. If you are using 2D painting, like Photoshop, you probably want to minimize seams. If you are using 3Dcoat, Substance Painter, or Mari, the number of seams are much less important, and orientation can be for best fit (maximizing your texture area) rather than aligned.
Second attachment is entire unwrap done in Houdini with method suggested above. The group was done with polygon selection rectangle with the eye icon to avoid selecting the back of the model. The UV edit nodes basically just pull off the pedals to separate them (avoiding overlap).
Regarding mesh overlaps, you could prevent this entirely in one of two ways. Since you have a seam, you can add a blast or delete node and remove all polys on one side of the loop. Then create another blast node and delete the polys on the other side of the loop. Perform UV mapping separately on each part and then merge them together and pack the UVs.
The second way would be to use a UVedit node and either move the vertices or just break off the areas where there is overlap (the equivalent of adding an extra seam). (see attachment, done in Modo, but could have been done in Houdini with UVedit)
Coloring the mesh can actually be done in Houdini/Mantra without UVs at all, since you can ramp the point position or point normal to a color. But if you are doing proper UV's, it depends on how you plan to color your model. If you are using 2D painting, like Photoshop, you probably want to minimize seams. If you are using 3Dcoat, Substance Painter, or Mari, the number of seams are much less important, and orientation can be for best fit (maximizing your texture area) rather than aligned.
Second attachment is entire unwrap done in Houdini with method suggested above. The group was done with polygon selection rectangle with the eye icon to avoid selecting the back of the model. The UV edit nodes basically just pull off the pedals to separate them (avoiding overlap).
Edited by Island - July 25, 2020 19:49:40
Houdini Indie and Apprentice » Why is not this working? (UV Flatten/Seams)
- Island
- 340 posts
- Offline
Retopologizing reduces size easily from 30.5MB to 2MB.
I don't think Houdini is the best tool to use for complicated UV editing. In most dedicated uv unwrapping tools, one creates seams and does an initial unwrap. Then one hides the islands that one doesn't want to work with and relaxes or optimizes or reprojects the problematic island. Then one goes to the next island and does the same. Finally, everything is unhidden and then packed. The uvedit node in Houdini is not especially helpful in automating parts of this.
If you are on windows, the lab node for quadremesher would be a good purchase for fixing topology. There is a blender version, if your model originated there. The algorithm is the same as zbrush.
I don't think Houdini is the best tool to use for complicated UV editing. In most dedicated uv unwrapping tools, one creates seams and does an initial unwrap. Then one hides the islands that one doesn't want to work with and relaxes or optimizes or reprojects the problematic island. Then one goes to the next island and does the same. Finally, everything is unhidden and then packed. The uvedit node in Houdini is not especially helpful in automating parts of this.
If you are on windows, the lab node for quadremesher would be a good purchase for fixing topology. There is a blender version, if your model originated there. The algorithm is the same as zbrush.
Edited by Island - July 25, 2020 15:06:42
Houdini Indie and Apprentice » Why is not this working? (UV Flatten/Seams)
- Island
- 340 posts
- Offline
The model has problematic topology (and would be best retopologizing), but I think the main issue is that you should not have anything in the group box. Personally, I would use a UVproject node set to orthographic xy plane. If you want to fine tune it, make a much smaller loop for the part that is most non planar and use UV flatten on just that. Your best bet would be to use Zbrush for both retopologizing and UV mapping this sort of shape. Second best would be Rizom UV. Here is just the UVproject:
Edited by Island - July 25, 2020 13:34:24
Houdini Indie and Apprentice » Why is not this working? (UV Flatten/Seams)
- Island
- 340 posts
- Offline
There is something very wrong with that flatten. Can you post your hip file or just a bgeo with uv flatten node? It looks like all edges were selected as seams.
Edited by Island - July 25, 2020 00:47:56
Houdini Lounge » Houdini non-procedural modeling?
- Island
- 340 posts
- Offline
Houdini Lounge » Houdini non-procedural modeling?
- Island
- 340 posts
- Offline
Destructive modeling in Houdini works quite well. You even have the equivalent of Modo's action centers with the align options and clever use of the apostrophe key. Here is a hand model done with destructive modeling in Houdini. Typically, there are some extra loops and subsequent removal of the loops, as is sometimes done with other 3D programs when one changes one's mind.
Edited by Island - July 16, 2020 17:48:34
Houdini Indie and Apprentice » Rendering issue with houdini apprentice
- Island
- 340 posts
- Offline
Have you tried locking the camera to the view and then rotating the view? Is your render set to the camera you are manipulating?
Houdini Indie and Apprentice » No "lockdown" sale?
- Island
- 340 posts
- Offline
It is always on sale compared with other more expensive and more limited programs. Apprentice is free, if you want an incredible deal.
Technical Discussion » Very basic question about shadow mat
- Island
- 340 posts
- Offline
Brilliant! My mistake. I did not set one of the constants correctly. It works perfectly now.
Technical Discussion » Very basic question about shadow mat
- Island
- 340 posts
- Offline
Unfortunately that is worse. It does not render the shadow and the ground plane is completely transparent. Thanks for looking though.
-
- Quick Links