Horde3D

Hey guys,

I'm a bit stuck with a little project that I'm working on. I need to be able to change the transparency and colour of a material that I have applied to a scene node. After reading through a few related posts on this forum, I've come to the conclusion that I might have to create my own shader and declare a "uniform" variable to hold the colour and transparency that I want to render.

How do I go about doing this? I've written shaders before but I'm not sure I understand Horde's XML format for shaders. Also how do I ensure that a uniform variable that I've declared in the material.xml file is being passed to the shader?

Any help/advice is greatly appreciated.

Cheers,

Jarryd

A material.xml file looks like:



Your shader contexts then access the uniform by declaring it at as normal:

uniform vec4f myUniform;

The Data Format reference in the Horde3D manual covers this material in greater detail.

You can take a look at a palette recoloration technique I put up in the wiki under "Community Tutorials."

Thanks for the help! Managed to get my shader working!

Alright. Perhaps I spoke to soon.... . Let me clarify my problem first. I'm loading a resource as follows:


ResHandle modelRes = Horde3D::addResource( ResourceTypes::SceneGraph, "model.scene.xml", 0 );
NodeHandle modelNode = Horde3D::addNodes( RootNode, modelRes );

The model then loads and displays correctly using a custom shader that I've specified in the material.xml file. The shader is also properly accessing the values of the uniforms declared in the xml file.

My question is, how do I then modify these uniforms at runtime? The API seems to have commands that allow you to modify the material resource for a "mesh node" but not for a "scene graph" node.

Just a quick update. I've managed to use setMaterialUniform(materialRes,"particleColour",1.0,0.0,0.0,1.0) but that seems to change the uniforms for all scene nodes that use this material. Is there some way to set these uniforms on a "per mesh/node" basis?

I'm guessing I'll have to clone the material resource in order to do that :S.

You have to clone. A varying uniform is on my own to-do list, if you'd like me to bounce you some code that does the trick (though it's a quirky proof of concept that will look nothing like a final write) then PM me your email address.