[GLSL] NVIDIA vs ATI shader problem

Florian Rammerstorfer · 2014-03-30T21:33:40

Hello! I am trying to get my engine running on ATI/AMD(previously i only ran it on NVIDIA). My shader uses diffuse lighting to render a sphere and a plane(both with same material). This works totally fine on NVIDIA graphics cards. On ATI it compiles, but shows really weird results when executed. The sphere appears to have some issue with fetching texture and the plane does not appear at all. I also tried compiling it with AMDs Shader Analyzer and it did compile without errors or warnings. Here is the vertex shader: uniform mat4 gWVP; uniform mat4 gNormalMatrix; uniform mat4 gModelViewMatrix; in vec3 inPosition; in vec3 inNormal; in vec2 inTexcoord; in vec3 inTangent; out vec2 vTexcoord; //all of these are in eyespace out vec3 vPosition; out vec3 vNormal; out vec3 vTangent; void main() { gl_Position = gWVP * vec4(inPosition,1.0); vNormal = normalize((gNormalMatrix * vec4(inNormal,0.0)).xyz); vTangent = normalize((gNormalMatrix * vec4(inTangent,0.0)).xyz); vPosition = (gModelViewMatrix * vec4(inPosition,1.0)).xyz; vTexcoord = inTexcoord; } and fragment shader: #version 130 const int LIGHT_TYPE_NONE = 0; const int LIGHT_TYPE_DIRECTIONAL = 1; const int LIGHT_TYPE_POINT = 2; struct Light{ int lightType; vec3 position; vec4 diffuse; float intensity; float constantAttenuation; float linearAttenuation; float quadraticAttenuation; }; const int NUM_LIGHTS = 4; uniform Light gLights[NUM_LIGHTS]; uniform vec4 gGlobalAmbient; vec4 calculateDiffuse(Light light, vec4 surfaceColor, vec3 normal, vec3 lightDir) { vec4 outColor = vec4(0.0); vec3 normalizedLightDir = normalize(lightDir); float NdotL = max(dot(normal,normalizedLightDir),0.0); if(light.lightType == LIGHT_TYPE_DIRECTIONAL) { if (NdotL > 0.0) { outColor += surfaceColor * light.diffuse * light.intensity * NdotL; } }else if(light.lightType == LIGHT_TYPE_POINT) { float dist = length(lightDir); if (NdotL > 0.0) { float attenuation = 1.0 / (light.constantAttenuation + light.linearAttenuation * dist + light.quadraticAttenuation * dist * dist); outColor += surfaceColor * light.diffuse * light.intensity * attenuation * NdotL; } } return outColor; } uniform sampler2D gMainTexture; in vec2 vTexcoord; in vec3 vPosition; in vec3 vNormal; in vec3 vTangent; out vec4 outColor; void main (void) { vec4 texDiffuse = texture(gMainTexture,vTexcoord); vec3 normal = normalize(vNormal); vec3 tangent = normalize(vTangent); vec3 bitangent = cross(normal, tangent); mat3 tangentSpaceMatrix = mat3( tangent.x, bitangent.x, normal.x, tangent.y, bitangent.y, normal.y, tangent.z, bitangent.z, normal.z ); //ambient outColor = texDiffuse * gGlobalAmbient; for(int i = 0;i<NUM_LIGHTS;i++) { vec3 lightDir = vec3(0.0); if(gLights[i].lightType == LIGHT_TYPE_DIRECTIONAL) { lightDir = normalize(tangentSpaceMatrix * gLights[i].position); }else if(gLights[i].lightType == LIGHT_TYPE_POINT) { lightDir = tangentSpaceMatrix * (gLights[i].position - vPosition); } if(gLights[i].lightType != LIGHT_TYPE_NONE) { outColor += calculateDiffuse(gLights[i],texDiffuse,vec3(0.0,0.0,1.0),lightDir); } } } I hope someone can point out the issue to me or help me find a solution to debug it(since its no compiler error). Thanks in advance!

Graphics and GPU Programming Programming

Started by Florian22222 March 28, 2014 07:33 PM

16 comments, last by TheChubu 10 years ago

JohnnyCode

1,084

March 30, 2014 01:15 AM

It gives a compiler error without specified #version directive. I decided on version 130 to support as much hardware as possible.

thank god!

TheChubu

9,484

March 30, 2014 02:03 AM

thank god!

Praise the lord!

"I AM ZE EMPRAH OPENGL 3.3 THE CORE, I DEMAND FROM THEE ZE SHADERZ AND MATRIXEZ"

My journals: dustArtemis ECS framework and Making a Terrain Generator

Florian22222

618

Author

March 30, 2014 07:51 AM

So does anyone have a clue why the line posted above would make a problem on ati but not on NV?

Hodgman

52,717

March 30, 2014 08:16 AM

I tracked at least one of the issues down to this line in the vertex shader:
vNormal = normalize((gNormalMatrix * vec4(inNormal,0.0f)).xyz);
If I uncomment it, the vertex positions are correct. As soon as I don't uncomment this line the plane is not being rendered at all and the sphere's texcoords are wrong.

Commenting out that line will also cause the vNormal, gNormalMatrix and inNormal variables to be optimized away.

Try replacing it with lines that use them in some other way, sugh as vNormal = inNormal; etc, and see if you can find other variations which are ok/broken.

Also, one other thing that might be relevant is how your vertex attributes are being supplied to the vertex shader from the CPU side..

. 22 Racing Series .

Florian22222

618

Author

March 30, 2014 09:47 AM

Ok I finally solved it with the help of you guys!

The problem was in the attribute locations in the vertex shader. NV automatically generates those according to the order in which the attributes where defined, while ATI needs to have the explicit layout(location = index) in front of each attribute. Also I switched to #version 330 otherwise those layout() identifiers are not available. The version change is no problem since i want to implement a deferred renderer in the next step anyway.

Again, thank you for your help!

Tasaq

1,530

March 30, 2014 10:18 AM

This is very annoying thing when it comes to shaders :\ I remeber in my early days when I tested my application on Nvidia card everything was ok, and I had problems with AMD. What solved my problems was changing doubles to floats (i.e. changing 0.0 to 0.0f).

Depending on the version, GLSL requires you to put the f suffix on there. nVidia's GLSL compiler deliberately accepts invalid code, whereas AMD's strictly follows the specification. This is a good way for nVidia to use us developers as a marketing/FUD weapon, spreading rumours that AMD has bugs...

Seeing that GLSL code is compiled by your graphics driver, which may or may not be different to your user's driver, it's a good idea to run your code through an external tool to ensure it's valid, such as ShaderAnalyzer, glsl-optimizer, the reference compiler, etc...

It was during the time I used shaders for the very first time and 'I had no idea what I was doing' :). Back then I was using shader designer btw.

_the_phantom_

11,263

March 30, 2014 08:11 PM

NV automatically generates those according to the order in which the attributes where defined, while ATI needs to have the explicit layout(location = index) in front of each attribute.

If you don't specify the order (so no layout or pre-330) then you should query the data from the compiled/linked program as the driver is free to do as it likes.

TheChubu

9,484

March 30, 2014 09:33 PM

If you don't specify the order (so no layout or pre-330) then you should query the data from the compiled/linked program as the driver is free to do as it likes.

This. No explicit layout == query all the positions from the application side after you make the program. Its the standard way to do that in OpenGL, regardless of what NV driver does.

"I AM ZE EMPRAH OPENGL 3.3 THE CORE, I DEMAND FROM THEE ZE SHADERZ AND MATRIXEZ"

My journals: dustArtemis ECS framework and Making a Terrain Generator

[GLSL] NVIDIA vs ATI shader problem

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