Bug in nvidia glsl compiler?

[grisha]

void main()
{
gl_Position = ftransform();
#if 1
float d = gl_ProjectionMatrix[3][2]*gl_Normal.x-gl_ProjectionMatrix[2][2];
#else
float d = -gl_ProjectionMatrix[2][2]+gl_ProjectionMatrix[3][2]*gl_Normal.x;
#endif
gl_FrontColor = vec4( d );
} Both variants of calculation of d should give same result, isn't it? With second variant '-' operator is ignored. Just try it yorself - by changing '#if 1' to '#if 0'.

driver version: 77.72

[grisha]

Is anybody able to reproduce it?

these two shaders produce same asm output.

Shader 1:

void main()
{
gl_Position = ftransform();
float d = gl_ProjectionMatrix[2][2]+gl_ProjectionMatrix[3][2]*gl_Normal.x;
gl_FrontColor = vec4( d );
} Shader 2:

void main()
{
gl_Position = ftransform();
float d = -gl_ProjectionMatrix[2][2]+gl_ProjectionMatrix[3][2]*gl_Normal.x;
gl_FrontColor = vec4( d );
} Asm output (enabled in nvemulate) for both:


!!VP2.0
# cgc version 1.3.0001, build date Jun 15 2005 17:58:26
# command line args:
#vendor NVIDIA Corporation
#version 1.0.02
#profile vp30
#program main
#semantic gl_ProjectionMatrix
#semantic gl_ModelViewProjectionMatrixTranspose
#var float3 gl_Normal : $vin.NORMAL : ATTR2 : -1 : 1
#var float4 gl_Vertex : $vin.POSITION : ATTR0 : -1 : 1
#var float4 gl_Position : $vout.POSITION : HPOS : -1 : 1
#var float4 gl_FrontColor : $vout.COLOR0 : COL0 : -1 : 1
#var float4x4 gl_ProjectionMatrix : : c[0], 4 : -1 : 1
#var float4x4 gl_ModelViewProjectionMatrixTranspose : : c[4], 4 : -1 : 1
BB1:
DP4 o[HPOS].w, v[0], c[7];
DP4 o[HPOS].z, v[0], c[6];
DP4 o[HPOS].y, v[0], c[5];
DP4 o[HPOS].x, v[0], c[4];
MUL R0.x, v[2], c[3].z;
ADD o[COL0], R0.x, c[2].z;
END
# 6 instructions, 1 R-regs

[sqrt[-1]]

If it looks like a bug, acts like a bug, it is a ....

It certainly appears it is just ignoring the -(negate operator)

I think you are going to need cass or another nvidia guy to give a difinite answer. (Have you emailed them about it?)

Have you tried assigning the uniforms to a tempoary value before using them. It should not make any difference but who knows...

[speedy]

Consider trying beta drivers from ie. www.guru3d.com.. (http://www.guru3d.com..) BETA 80.40 seem to have quite good behaving GLSL implementation. (and luckily only one which works for me at the moment) YMMV.