Bizzar nVidia compile error

OpenGL
1

What does this mean:

error C5108: unknown semantics "ATTR0.xyz" specified for "fragTexCoord1"

This is from the linking of a vertex and fragment program. The line it refers to is:

varying vec2 fragTexCoord1;

What is nVidia’s compiler even talking about? What is a “semantic” anyway, and where does this “ATTR0.xyz” even come from?

2

The error message almost seems to suggest that perhaps an attribute binding has gone wrong, but I’m not sure how that relates to that varying line…

Which driver version are you using? Could you post more of the shader?

3

i assume ATTR0.xyz is attribute 0 which is always vertex for nvidia cards

with nvemulate u can turn on generate asm output (which i just did + got from one of my shaders)
#var float4 gl_Vertex : $vin.POSITION : ATTR0 : -1 : 1

btw this forum needs to fix up displaying code of one line

4

I can’t honestly say what was wrong with the program, but I can say how I fixed it. And it is truly bizzare.

Here’s the original vertex shader.

attribute vec2 position2d;
attribute vec2 texCoord2d;

varying vec2 fragTexCoord1;

void main()
{
	vec4 realPos;
	realPos.xy = position2d;
	realPos.z = 0.0;
	realPos.w = 1.0;
	
	gl_Position = gl_ModelViewProjectionMatrix * realPos;
	fragTexCoord1 = texCoord2d;
}

Here’s the original fragment shader.


uniform vec4 color;
uniform sampler2D tex1;

varying vec2 fragTexCoord1;

void main()
{
	gl_FragColor = color * texture2D(tex1, fragTexCoord1);
}

In addition to the error I posted, I also got a warning in the fragment shader about the use of fragTexCoord1. That is, it is a vec2 and texture2D takes a vec3. However, it was just a warning.

Here’s the change to the fragment program that made the vertex program error go away (and yes, I’m sure the error appeared in the vertex program):


uniform vec4 color;
uniform sampler2D tex1;

varying vec2 fragTexCoord1;

void main()
{
	vec3 tempVal = vec3(fragTexCoord1.x, fragTexCoord1.y, 0.0f);
	gl_FragColor = color * texture2D(tex1, tempVal);
}

The best guess I can make is that when the fragment shader compiled, it silently changed the varying fragTexCoord1 from a vec2 to a vec3 (why it should believe that silently changing the type of a varying is ever OK is beyond me). Of course, when I go to link it to a vertex shader that thinks fragTexCoord1 is a vec2, it breaks. With a very obtuse error. That doesn’t actually point to the problematic line.

I’m grateful for nVidia having a half-way decent glslang compiler, but it would be more decent if the error messages for that compiler actually spoke glslang and not ARB_vertex_program or HLSL.

5

Uh, texture2D takes a vec2 - from the spec:

vec4 texture2D (sampler2D sampler, vec2 coord [, float bias] )

I just tried your original shader and it compiles fine 162.18 drivers Geforce 8600

6

I just tried your original shader and it compiles fine 162.18 drivers Geforce 8600

That’s the thing. I got an 8800GT a few days ago. Before then, I was running a 6600. It compiled perfectly fine on the 6600, but once I installed the 8800GT with new drivers it stopped liking it.

I’m guessing that this is some kind of driver bug.

7

In Cg, a semantic is a label applied to an input or output variable telling the GPU where that value comes from or how it should be used. Some semantics are TEXCOORD0, COLOR, TEXUNIT0, POSITION, etc.

I don’t know GLSL, but I suspect they’re essentially the same as “attributes” based on the usage in this thread.

8

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