[Radiance-general] Ambient exclude transfomed materialin instances

[Giulio Antonutto]

some UV stuff here and hopefully not too many mistakes...

 

http://web.mac.com/geotrupes/iWeb/Main%20site/RadBlog/3690C181-7F9F-43AD
-B5B2-A5D239AD503E.html

 

G.

 

 

________________________________

From: radiance-general-bounces at radiance-online.org
[mailto:radiance-general-bounces at radiance-online.org] On Behalf Of Jack
de Valpine
Sent: 03 April 2007 18:10
To: Radiance general discussion
Subject: Re: [Radiance-general] Ambient exclude transfomed materialin
instances

 

Hi Iebele,

To use local u,v coordinate mapping (Lu,Lv) you need to use obj2mesh
rather than obj2rad.

Here is the process for making a mesh element:

Define mats.tree.rad using simple materials first as an example. The
names of the materials must correspond to the names of the materials
indicated for the .obj geometry (take a look in the .mtl file to get the
names).

mats.tree.rad:

void plastic Bark
0
0
5 1 1 1 0 0

void plastic Leaf
0
0
5 1 1 1 0 0

Generate tree.rtm as follows:

obj2mesh -a mats.tree.rad tree.obj > tree.rtm

Creat tree.mesh.rad as follows:

tree.mesh.rad:

void mesh tree
1 tree.rtm
0
0

Test you mesh:

objview tree.mesh.rad

Now lets apply more complex materials using local u,v coordinate
mapping. To do this you need the following image data:

1.	bark.pic
2.	aspect ratio for bark.pic (y/x), lets call it <arB>
3.	leaf.pic
4.	aspect ration for leaf.pic (y/x), lets call it <arL>
5.	leaf.matte.pic - this is the alpha/matte channel for the leaf.
The correct way to setup the matte is  for white to represent the leaf
and black to represent what is not the leaf. This means that you may
have to invert the matte the comes from xfrog.

	Now lets create the complex materials in mats.tree.rad

	mats.tree.rad:

	#BARK definition
	void colorpict bark.tile
	7 red green blue Bark.pic . frac(Lu) frac(Lv)*<arB>
	0
	0
	
	bark.tile plastic Bark
	0
	0
	5 1 1 1 0 0
	
	#LEAF definition
	void colorpict leaf.tile
	7 red green blue Bark.pic . frac(Lu) frac(Lv)*<arL>
	0
	0
	
	leaf.tile plastic leaf.map
	0
	0
	5 1 1 1 0 0
	
	leaf mixpict Leaf
	7 leaf.map void green leaf.matte.pic . frac(Lu) frac(Lv)*<arL>
	0
	0

	Now recompile your mesh:

	obj2mesh -a mats.tree.rad tree.obj > tree.rtm

	Now view it:

	objview tree.mesh.rad

You should add Bark and Leaf to your ambient exclude file/list if you do
not want them in the ambient calculation. You can use tree.mesh.rad
along with replmarks, xform or some other method to deploy the tree
object in the scene.

This should work fine. Let me know if you have any questions.

-Jack

Gregory J. Ward wrote: 

Hi Iebele, 

I can't be much help on this, as I'm not familiar with the model, but
the general idea with local coordinates is that you don't have to do the
mapping yourself.  It's supposedly handled by the mesh generation
software, and isn't affected by transformations as a global coordinate
mapping would be. 

I hope this is a helpful clue, as it's about all I have to offer. 
-Greg 




From: iebele <info at iebele.nl> <mailto:info at iebele.nl>  
Date: April 3, 2007 8:39:12 AM PDT 

Thanks Greg an Jack for your excellent and very  helpfull suggestions. 

I now have succesfully converted the .obj file to rad, using obj2rad (
polytrans did indeed work with Xfrog obj-files, but meshlab did not
accept these files Lars ). 

However I can't get the mapping right. I've tried a lot, but with no
succes. Would you please share with me an example of the materials you
use for the bark and the leaves? 

I just don't really understand when and how to use Lu and Lv  or
frac(Lu) and frac(Lv) in the colorpict modifier and how these can ever
be placed  in a reasonable way on each triangle in the output of
obj2rad, which in my case is like : 

leaf_col_leaf2 polygon leaf22836.60976 
0 
0 
9 
        -0.250204           0.195593             13.838 
         -1.00383          -0.956752            13.8816 
         -1.21881           -0.19178            13.5622 

I never really understood the meaning of texture-coordinates, but at
this time I feel that is what  is  missing here. 

Is there a difference in using obj2rad and obj2mesh for this purpose ? I
tried both but with the some odd results concerning the coordinate
mapping. 

-Iebele 


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