Thanks for your input, both of you. It turns out that after more than a week of tinkering with it, today was the day I finally made progress on the project.
I got the second glass, the one with triangular geometry made from a sphere mesh, to look like my first glass by changing a Convert SOP “convert to” prameter from polygon to mesh. I was using this Convert SOP directly after my Sphere SOP because I wanted each triangular face to have its own surface normal, but I guess in converting from mesh to polygon Houdini somehow doubles the number of faces? I'm still not sure what's going on here.
I've also mitigated my second problem enough that I can actually render most of the frames. The Cookie SOP union between the RealFlow mesh and the glass would fail for most of the frames–the RealFlow mesh or the glass would disappear–but I can now get most of the frames to work by lowering the 3D tolerance to 0.0000101 (the lowest nonzero value). It turns out the problem is not wrong-direction normals in the RealFlow mesh, but something related to the minimum resolvable distance between the mesh and the glass (I think).
About examing .geo files, the only way I was able to get a cube into RealFlow was to write it by hand. I haven't tried to get my glass into RealFlow yet, but I'd hate to hand code 1500+ points! RealFlow seems really picky about what it imports, and not just any triangular geometry will do. I wonder if other 3D packages have such difficulty making RealFlow-readable geometry?
So now my computer will once again be occupied 24/7: rendering at night, and letting me figure out how to write displacement shaders during the day…
Mike
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Technical Discussion » problems: geometry & refraction; Cookie vs Boolean SOP
- mikela
- 27 posts
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Technical Discussion » problems: geometry & refraction; Cookie vs Boolean SOP
- mikela
- 27 posts
- Offline
I thought I would post some renders of the first problem I was having, of the geometry that did not want to refract properly:
This glass looks OK as far as I can tell, and was made with two capped tubes and a cookie SOP, but, alas, does not have triangular geometry:
This glass is made from a sphere mesh whose points have been pushed and pulled into position. It doesn't seem to pass light at all despite having the same shaders and the same number of surfaces for incident light to pass through.
This glass looks OK as far as I can tell, and was made with two capped tubes and a cookie SOP, but, alas, does not have triangular geometry:
This glass is made from a sphere mesh whose points have been pushed and pulled into position. It doesn't seem to pass light at all despite having the same shaders and the same number of surfaces for incident light to pass through.
Technical Discussion » problems: geometry & refraction; Cookie vs Boolean SOP
- mikela
- 27 posts
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I've been playing with the RealFlow ROP/IFD plugin (thanks, Mark!) and wanted to put a tweaked version of the Real Flow “2 Fluids” example into Houdini as an excercise. I've had no problems importing particles or meshes, but I have had a few unrelated problems due to my lack of experience with Houdini:
Making a glass with triangular geometry (necessary for RealFlow import)and the correct refraction characteristics. I made my first glass with two capped tubes and a Cookie SOP, hoping to simply use the convert SOP to convert to triangular geometry, but the geometry would not convert. I made my second glass out of a sphere mesh, moving the points around until I got the right shape. But while I now have triangular geometry, the second glass won't refract light naturally like the first (or even reflect the same in OpenGL), and I don't have a clue why it won't. Help! My .hipnc file is here [odysseus.anderson.name]
Second question: how do I make a Cookie SOP union act like a Boolean SOP union? The Boolean SOP cuts holes in the geometry just the way I want, but won't work if the surfaces are not closed (as some of the RealFlow meshes are not). So I suppose one solution is to close the geometry and use the Boolean SOP…but I don't know how. The Cookie SOP is sensitive to surface normals, which I suppose is how it's able to deal with open surfaces, but then I need a way to filter out the parts of the mesh with the wrong normals. Any ideas?
Mike
Making a glass with triangular geometry (necessary for RealFlow import)and the correct refraction characteristics. I made my first glass with two capped tubes and a Cookie SOP, hoping to simply use the convert SOP to convert to triangular geometry, but the geometry would not convert. I made my second glass out of a sphere mesh, moving the points around until I got the right shape. But while I now have triangular geometry, the second glass won't refract light naturally like the first (or even reflect the same in OpenGL), and I don't have a clue why it won't. Help! My .hipnc file is here [odysseus.anderson.name]
Second question: how do I make a Cookie SOP union act like a Boolean SOP union? The Boolean SOP cuts holes in the geometry just the way I want, but won't work if the surfaces are not closed (as some of the RealFlow meshes are not). So I suppose one solution is to close the geometry and use the Boolean SOP…but I don't know how. The Cookie SOP is sensitive to surface normals, which I suppose is how it's able to deal with open surfaces, but then I need a way to filter out the parts of the mesh with the wrong normals. Any ideas?
Mike
Technical Discussion » Curve SOP: referencing coordinates
- mikela
- 27 posts
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again, thanks for the help.
I guess I really didn't read those expression docs all that well! It was right there the whole time. It still seems, though, that some expressions are undocumented. For example, nearpoint() is not defined anywhere in the 6.0 docs that I can tell, and I haven't been able to get it to work yet. If it returns the position or the vector to the position on a NURBS curve closest to the given point, it's just what I've been looking for.
I suspect most of my channel reference problems will be solved once I master CHOPs, so I'll bother you guys again after I've thoroughly read those docs :?
BTW, Houdini is my first 3D package. My workflow so far is simply the way I think you should be able to do things, and for the most part Houdini has been happy to oblige. Anybody get it to do fluid dynamics?
I guess I really didn't read those expression docs all that well! It was right there the whole time. It still seems, though, that some expressions are undocumented. For example, nearpoint() is not defined anywhere in the 6.0 docs that I can tell, and I haven't been able to get it to work yet. If it returns the position or the vector to the position on a NURBS curve closest to the given point, it's just what I've been looking for.
I suspect most of my channel reference problems will be solved once I master CHOPs, so I'll bother you guys again after I've thoroughly read those docs :?
BTW, Houdini is my first 3D package. My workflow so far is simply the way I think you should be able to do things, and for the most part Houdini has been happy to oblige. Anybody get it to do fluid dynamics?
Technical Discussion » Curve SOP: referencing coordinates
- mikela
- 27 posts
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hello again,
still learning Houdini…
So many things I want to do seem so simple, but when I go to do them, the OPs I've used in the tutorials won't work for those purposes. For the last several hours I've been trying to copy geometry objects onto points of a curve SOP. Simple enough…but I also need to access the (x,y,z) coordinates of each point in the curve SOP from the copy SOP.
The curve SOP does not appear to allow this. For example, when I copy values from the curve spreadsheet, I can only copy the value and not the variable reference. Any suggestions? Do I have to use a different transform SOP for every point on a curve filled with (0,0,0) points?
Does anyone have a comprehensive guide to expression syntax and variables? The help .pdf doesn't seem too comprehensive to me, but it could just be my naivete…
still learning Houdini…
So many things I want to do seem so simple, but when I go to do them, the OPs I've used in the tutorials won't work for those purposes. For the last several hours I've been trying to copy geometry objects onto points of a curve SOP. Simple enough…but I also need to access the (x,y,z) coordinates of each point in the curve SOP from the copy SOP.
The curve SOP does not appear to allow this. For example, when I copy values from the curve spreadsheet, I can only copy the value and not the variable reference. Any suggestions? Do I have to use a different transform SOP for every point on a curve filled with (0,0,0) points?
Does anyone have a comprehensive guide to expression syntax and variables? The help .pdf doesn't seem too comprehensive to me, but it could just be my naivete…
Technical Discussion » Orbit POP: how do I use a line as the center?
- mikela
- 27 posts
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the answer turned out to be simple, but it still took some reading and trial & error to find it:
center_y=$TY
I just didn't expect that $TY would reference each individual particle's y position…
thanks for the lead!
center_y=$TY
I just didn't expect that $TY would reference each individual particle's y position…
thanks for the lead!
Technical Discussion » Orbit POP: how do I use a line as the center?
- mikela
- 27 posts
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I'm just learning Houdini (this is my first post here) so I'm hoping someone will find this question obvious and help me out…
The Orbit POP has many different center types, but they all seem to be ways to define a point about which everything orbits. But what if I want everything to orbit about the axis without introducing axial motion, to simply orbit around a line? Like a stack of pancakes on a turntable…
Mike Anderson
The Orbit POP has many different center types, but they all seem to be ways to define a point about which everything orbits. But what if I want everything to orbit about the axis without introducing axial motion, to simply orbit around a line? Like a stack of pancakes on a turntable…
Mike Anderson
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