View Full Version : glsl and pn_triangles

01-20-2005, 02:39 AM
How do I export normals from glsl vertex shader in order to make ATI_pn_triangles work? Everything looks fine using fixed pipeline but using glsl vertex shader results in some polygons missing (R9600, Catalyst 05.1). Is it a bug or It's not possible to make these two extensions to work together?

01-20-2005, 05:09 AM
- pn_triangles supported in hardwsare only in ATI R2x0(which not suppor GLSL).
- R3x0(including R9600)/R4x0 - doesn't support it(may be in software).

01-20-2005, 05:46 AM
- R3x0(including R9600)/R4x0 - doesn't support it(may be in software).

You have to enable it via Control Panel. After that you can see ATI_pn_triangles in extensions list.

01-20-2005, 04:08 PM
Are you asking how to tell it which attribute is a position and which ones are normals? I think the only way to do that is to actually use the position and normal attributes (and therefore glVertexPointer and glNormalPointer).

01-20-2005, 11:19 PM
I'm doing all of that. I'm passing data to OpenGL as arrays (both vertex a normals). Vertex shader (glsl) looks like that:

varying vec3 n;
gl_Position = ftransform();
//gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
n = normalize(gl_NormalMatrix * gl_Normal);

The only problem is that some polygons inside scene are missing. Without vertex shading everything is allright.

I've read pn_triagles and there's written:
(3) How does this extension interact with the EXT_vertex_shader and ARB_vertex_program programmable vertex shader extensions?

RESOLVED: The PN Triangle tessellation algorithm requires the presence of both vertex position and normal. Therefore, if an application enables PN Triangle tessellation and has a programmable vertex shader enabled, that shader should export the fixed-function equivalent of position and normal. "

I simply don't know how to export normals from vertex shader. There's no gl_OutputNormal. The spec si written agains ARB_vertex_program but there's no "result.normal" either.

Stange thing is that I have got the same shader and same geometry rendered via DirectX + HLSL and
it's working...