Found 16 posts.
Search results Show results as topic list.
Technical Discussion » Light instancing shadow mask
- dan.baciu
- 30 posts
- Offline
Hello everybody.
I was trying to instance (point instancing) a subnet which contains a light and some geometry.
Together they form a lamp rig of sorts (a neon lamp)
Now, I want a part of the lamp geometry inside the subnet to not cast shadows from the light,
and I can set this using the “Shadow Mask” option of the light.
The problem is that this do not work with instancing (or point instancing).
I don't know how to make every instanced light to not cast shadows from it's corespondent instanced geometry.
This doesn't work even if I make a HDA out of this subnet (which is the goal anyway).
Also, It seems that I can't see the contains of the subnet (light OR geo)
in the viewport in case of instancing, why is that?
In the end, the goal is to make a lamp asset (together with light and geometry)
that I can also instance on many points in a scene.
How should I approach this?
Technical Discussion » Orienting normals
- dan.baciu
- 30 posts
- Offline
You are aware that to have a complete description of orientation you need at least a normal and an up vector. The normal should point along the curve and the up vector defines the direction perpendicular to the curve in this case.
Looky here: http://www.sidefx.com/docs/houdini14.0/copy/instanceattrs [sidefx.com]
Looky here: http://www.sidefx.com/docs/houdini14.0/copy/instanceattrs [sidefx.com]
Technical Discussion » random UV transform
- dan.baciu
- 30 posts
- Offline
In a for each loop you can use an expression like rand(stamp(“../”, “FORVALUE”, 0)*733.73).
This way the rand function will generate a random offset using the iteration number times some other number (for variation) as a seed.
So you can have for U rand(stamp(“../”, “FORVALUE”, 0)*733.73)
and for V rand(stamp(“../”, “FORVALUE”, 0)*328.42)
This way the rand function will generate a random offset using the iteration number times some other number (for variation) as a seed.
So you can have for U rand(stamp(“../”, “FORVALUE”, 0)*733.73)
and for V rand(stamp(“../”, “FORVALUE”, 0)*328.42)
Houdini Lounge » Problem with bounding boxes
- dan.baciu
- 30 posts
- Offline
The default sphere is a “primitive” sphere, meaning that it is described by only a center position and a radius (what we see in the viewport is only a representation).
Given that the sphere is only a point, it becomes clear that the bounding box algorithm doesn't have enough data to work properly and gives erroneous results.
Try with a nurbs sphere for example, it should work much better.
Given that the sphere is only a point, it becomes clear that the bounding box algorithm doesn't have enough data to work properly and gives erroneous results.
Try with a nurbs sphere for example, it should work much better.
Houdini Lounge » $PT in "carve" node
- dan.baciu
- 30 posts
- Offline
If you have to “translate” the point expression it would be something like this:
Give me a component of an attribute of a point of a certain geometry.
In your case is something like “give me component 0 of ”growth" attribute of point ??????? of node vopsop23
Point number is undefined. $PT makes no sense in this case (for carve sop).
What exactly are you trying to achieve?
Give me a component of an attribute of a point of a certain geometry.
In your case is something like “give me component 0 of ”growth" attribute of point ??????? of node vopsop23
Point number is undefined. $PT makes no sense in this case (for carve sop).
What exactly are you trying to achieve?
Houdini Indie and Apprentice » a value returned by random expression
- dan.baciu
- 30 posts
- Offline
Houdini Indie and Apprentice » a value returned by random expression
- dan.baciu
- 30 posts
- Offline
I think rand() is going to return a number in the 0 to 1 range. You can use fit01() to map that value to a range defined by two arbitrary numbers.
Technical Discussion » Split poly line at a point
- dan.baciu
- 30 posts
- Offline
You can use carve SOP. Check “Second U” and set it at 1. Check both “Keep Inside” and “Keep Outside”. For “First U” you need an expression. To cut at exact point position (on curve) you need to divide 1 (parametric length of the curve) by the number of points, and then multiply this with the number of the point where you want to cut.
Something like this (for an open curve):
1/(npoints(“../” + opinput(“.”, 0))-1) * 9
The last number (9) is the number of the point where the curve will split
npoints(“../” + opinput(“.”, 0)) returns the number of points in the node fed into the first input of the current node
Something like this (for an open curve):
1/(npoints(“../” + opinput(“.”, 0))-1) * 9
The last number (9) is the number of the point where the curve will split
npoints(“../” + opinput(“.”, 0)) returns the number of points in the node fed into the first input of the current node
Technical Discussion » Group primitive groups if not connected ?
- dan.baciu
- 30 posts
- Offline
I don't understand, what's wrong with connectivity/partition?
Maybe you aren't describing the problem properly…
Why do you want to merge groups together? Not to mention that (if I look at your first post) you don't have a clear rule to do that. If what you need is to group chunks of separated primitives (this is what I understand by “I want to merge groups together if they don't share edges in common”) then connectivity/partition is what you need. You don't need any existing groups for that. You can discard them.
Maybe you aren't describing the problem properly…
Why do you want to merge groups together? Not to mention that (if I look at your first post) you don't have a clear rule to do that. If what you need is to group chunks of separated primitives (this is what I understand by “I want to merge groups together if they don't share edges in common”) then connectivity/partition is what you need. You don't need any existing groups for that. You can discard them.
Technical Discussion » create displacement map from houdini
- dan.baciu
- 30 posts
- Offline
Here, try this. It renders the height map in the red channel. You can use the green and blue for other purposes (object id's, etc)
Work in Progress » Roof Generator
- dan.baciu
- 30 posts
- Offline
Hello guys. This is a part of the workflow using the roof generator to build roofs.
https://vimeo.com/58213385 [vimeo.com]
https://vimeo.com/58213385 [vimeo.com]
Work in Progress » Roof Generator
- dan.baciu
- 30 posts
- Offline
Thanks for the appreciation.
Well, it's basically the straight skeleton of a polygon (building outline).
Here you'll find more details about this:
http://vterrain.org/Culture/BldCity/Roof/index.html [vterrain.org]
http://www.sable.mcgill.ca/~dbelan2/roofs/roofs.html [sable.mcgill.ca]
I have some updates on this thing since the last posts
(which was kind of long time ago)
Now it can generate roofs with arbitrary slope section (think Angkor Wat).
The UV mapping is ok now either.
Also I worked on some structure for the roof (rafters, ridges and such)
but it still needs some work.
Now I'm working on doing gable roofs, dormers etc…
Well, it's basically the straight skeleton of a polygon (building outline).
Here you'll find more details about this:
http://vterrain.org/Culture/BldCity/Roof/index.html [vterrain.org]
http://www.sable.mcgill.ca/~dbelan2/roofs/roofs.html [sable.mcgill.ca]
I have some updates on this thing since the last posts
(which was kind of long time ago)
Now it can generate roofs with arbitrary slope section (think Angkor Wat).
The UV mapping is ok now either.
Also I worked on some structure for the roof (rafters, ridges and such)
but it still needs some work.
Now I'm working on doing gable roofs, dormers etc…
Technical Discussion » Renderman Texture Coordinates
- dan.baciu
- 30 posts
- Offline
Technical Discussion » Renderman Texture Coordinates
- dan.baciu
- 30 posts
- Offline
Guys, I'm trying to render with renderman an igloo that I made in Mudbox.
I imported the igloo from an obj.file using file sop.
But the displacement map exported from Mudbox is not applied correctly on my model.
Something is wrong but I don't know what…
Any help will be fiercely appreciated.
I imported the igloo from an obj.file using file sop.
But the displacement map exported from Mudbox is not applied correctly on my model.
Something is wrong but I don't know what…
Any help will be fiercely appreciated.
Technical Discussion » polyBevel doesn't work on small objects
- dan.baciu
- 30 posts
- Offline
I encountered this problem also.
I think it is a problem with precision, or the lack of it, and yes, it seems like a Houdini's problem.
As you can see, your value (0.004, which is 4 milimeters) is hard to handle, it's too small (to many decimals after the point), so the algorithm is lacking the precision to function correctly.
A workaround that I found is to insert a transform node before the polyBevel, scale the geometry to 100, do the bevel (it's value will be 4.0) and after that insert another transform node and scale everything back.
PS:
This is raising the question: Which unit is best for 3d work? Meters? Centimeters? In artistic 3d programs , which generally don't have the double precision of, let's say, Autocad, is best to keep everything close to 1 unit. So, if you have islands to model, work in meters or even kilometers. If you have skyscapers, boats, houses, work in meters. If you have small things, details, etc, work in centimeters.
In XSI the default unit 1=10 centimeters, which is a better compromise between meters and centimeters, precision wise.
I think it is a problem with precision, or the lack of it, and yes, it seems like a Houdini's problem.
As you can see, your value (0.004, which is 4 milimeters) is hard to handle, it's too small (to many decimals after the point), so the algorithm is lacking the precision to function correctly.
A workaround that I found is to insert a transform node before the polyBevel, scale the geometry to 100, do the bevel (it's value will be 4.0) and after that insert another transform node and scale everything back.
PS:
This is raising the question: Which unit is best for 3d work? Meters? Centimeters? In artistic 3d programs , which generally don't have the double precision of, let's say, Autocad, is best to keep everything close to 1 unit. So, if you have islands to model, work in meters or even kilometers. If you have skyscapers, boats, houses, work in meters. If you have small things, details, etc, work in centimeters.
In XSI the default unit 1=10 centimeters, which is a better compromise between meters and centimeters, precision wise.
Technical Discussion » Fur rendering problem
- dan.baciu
- 30 posts
- Offline
Guys, the problem is more than serious.
Have you tried to render fur with Houdini installed on Linux?
It appears that this is the problem: Houdini on Linux.
If you try to render fur with a texture driving some attribute of the material,
(like color) the render stops randomly.
So even the default shader (textured_hair) won't render, because
it's using the “leopardskin.rat” texture by default.
If there are no textures used in the shader, it appears to be working.
I used Marschner Hair shader from the Exchange, the same thing.
If it uses a texture, the whole thing blows.
Also, it appears that this is related to micropolygon rendering, I'm not shure.
I tried this on an Ubuntu 10.04 installation, AND on a CentOS 6.0 installation.
On Windows everything seems to be ok.
This is really strange…
Have you tried to render fur with Houdini installed on Linux?
It appears that this is the problem: Houdini on Linux.
If you try to render fur with a texture driving some attribute of the material,
(like color) the render stops randomly.
So even the default shader (textured_hair) won't render, because
it's using the “leopardskin.rat” texture by default.
If there are no textures used in the shader, it appears to be working.
I used Marschner Hair shader from the Exchange, the same thing.
If it uses a texture, the whole thing blows.
Also, it appears that this is related to micropolygon rendering, I'm not shure.
I tried this on an Ubuntu 10.04 installation, AND on a CentOS 6.0 installation.
On Windows everything seems to be ok.
This is really strange…
-
- Quick Links