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appleGuy

OpenGL OpenGL Shader Basics

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Hi, Ive done a vertex and fragmemnt shader in render monkey. Imported the shade (copy and paste) into a resource file in vs2005 and tried to use it in a very basic way. The Program compiles however the shader doesnt seem to be applied at all. The shader specic code in the app is: [CODE]#define GLEW_STATIC #include <GL/glew.h> GLhandleARB v, f, p; glewInit(); if(GLEW_ARB_vertex_shader && GLEW_ARB_fragment_shader){ v = glCreateShaderObjectARB(GL_VERTEX_SHADER_ARB); f = glCreateShaderObjectARB(GL_FRAGMENT_SHADER_ARB); const char *vv = readFile("lambert.vert"); const char *ff = readFile("lambert.frag"); if( vv != NULL && ff != NULL){ glShaderSourceARB(v, 1, &vv, NULL); glShaderSourceARB(f, 1, &ff, NULL); glCompileShaderARB(v); glCompileShaderARB(f); delete [] vv; delete [] ff; p = glCreateProgramObjectARB(); glAttachObjectARB(p, v); glAttachObjectARB(p, f); glLinkProgramARB(p); glUseProgramObjectARB(p); glUniform1iARB(glGetUniformLocationARB(p, "cloudTexture"), 0); glUniform4fARB(glGetUniformLocationARB(p, "shaderAmbient"), 1.0f, 0.5f, 0.5f, 1.0f); glUniform4fARB(glGetUniformLocationARB(p, "shaderDiffuse"), 1.0f, 0.5f, 0.5f, 1.0f); glUniform3fARB(glGetUniformLocationARB(p, "lightPos"), 25.0f, 50.0f, -15.0f); } } [/CODE]In Draw Loop: [CODE]glUseProgramObjectARB(p); glActiveTextureARB(GL_TEXTURE0_ARB); //Draw Object to be shaded etc glUseProgramObjectARB(NULL); //Other Studd using legacy pipeline[/CODE]the shaders work find in render monkey so its not the actual shaders (i dont think) frag shader: [CODE]uniform vec4 shaderDiffuse; uniform vec4 shaderAmbient; //Link from vertex shader holds texture coords varying vec2 texCoord; //Link to <-vertexLight varying vec3 lightDirection; varying vec3 normal; //Cloud Texture Access (2d texture) uniform sampler2D cloudTexture; void main(void) { //Dot Light Direction with normalDirection (Facing Ratio) //Need to normalise to get value between 0->1 to get different diffuse values float facingRatio = dot(normalize(normal), normalize(lightDirection)); vec4 diffuseColour = texture2D(cloudTexture,texCoord); vec4 light1 = (diffuseColour * shaderDiffuse * facingRatio); gl_FragColor = light1 + (shaderAmbient * diffuseColour); } [/CODE]vertex shader: [CODE]//The Shader works per vertex //Used to pass through fixed pipeline to fragment shader varying vec2 texCoord; varying vec3 normal; //Artist Tools uniform vec3 lightPos; //Light Vector varying vec3 lightDirection; void main(void) { //Apply fixed pipeline vertex transformations gl_Position = ftransform(); //Multi texture coordinate for texture 0 texCoord = gl_MultiTexCoord0.xy; //Get Current Vertex Position (to subtract from lightPos to get the vector) //Mulitply my modelview to put vetex position into world coordinates vec4 objectPos = gl_ModelViewMatrix * gl_Vertex; //Apply the light position into the world space (convert to vec4 w = 1) //Finds <-vertexLight lightDirection = (gl_ModelViewMatrix * vec4(lightPos, 1)).xyz - objectPos.xyz; //Set Model Normals to be pass to fragment shader normal = gl_NormalMatrix * gl_Normal; }[/CODE]Im using glew, visualc++ (visual studio 2005) My gpu supports the latest shaders and gl2.0+ Does something need to be set for glew etc to work in vs2005 or is my code wrong. Ive set up glew in the linker and in the lib and include sections of vs Many Thanks For Your help this has been bugging me for a couple of days now Cheers -Alex

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Use source tags with [] around source...

I am assuming this project compiles fine? No errors? Any errors from GL about the GLSL code? Have you checked to make sure there is no crap at the end of the text files after the last set of brackets?

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Hi,

thanks for the tip.

No crap at the end of the shader files.

However i did run a an error check using glGetError()

I get a return value of 1280.

After looking it up it is a GL_INVALID_ENUM.

What does this mean?

Thanks For Your Help
-Alex

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GL_INVALID_ENUM means a lot of things, try to find out, which line generates the Error.

Just check after each line with GLenum vars, the glGetError().

Say which line generates the error, i say you why it is ;)

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well the 1280 error generates before glewInit()...so before any of the shader stuff

then i get a 1282 after glUseProgramObjectARB(p) which i think is an GL_INVALID_OPERATION

all the glUniform also have a 1282 but i think that is because of the glUseProgramObjectARB(p) error

I also get a 1282 after glUseProgramObjectARB(p) in the main draw loop

Thanks
-Alex

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Grab the output of glGetShaderInfoLog() after compiling and glGetProgramInfoLog() after linking. Those are usually your first stop for shader problems, they have quite verbose output.

Usage (my Java code):


// create and compile
shaderID = GL20.glCreateShader(type);
GL20.glShaderSource(shaderID, sourceBuffer);
GL20.glCompileShader(shaderID);

// check for error
IntBuffer error = BufferUtils.createIntBuffer(1);
GL20.glGetShader(shaderID, GL20.GL_COMPILE_STATUS, error);
if( error.get() == GL11.GL_FALSE) {
Kernel.log("Could not compile shader: " + filename);

// print error from info log
IntBuffer length = BufferUtils.createIntBuffer(1);
GL20.glGetShader(shaderID, GL20.GL_INFO_LOG_LENGTH, length);
ByteBuffer infoLog = BufferUtils.createByteBuffer(300);
GL20.glGetShaderInfoLog(shaderID, length, infoLog);
Kernel.log(StringHelper.byteBufferToString(infoLog));
Kernel.shutdown(1);
}



I'm not 100% sure but you are using texCoord = gl_MultiTexCoord0.xy; in a way I've not encountered before, in the vertex shader. Not sure if it gets interpolated correctly. Also you're not using OpenGL lighting variables (RenderMonkey really needs to provide support for those, it's a joke not to have them. Bad ATI) but it does seem like you set every variable you needed to for your own lighting.

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Ok from the a call after vertex shader compile:

"Vertex shader failed to compile with the following errors:
ERROR: 0:35: '<' : syntax error parse error
ERROR: 1 compilation errors. No code generated."

from fragment shader compile:

"Fragment shader failed to compile with the following errors:
ERROR: 0:30: '<' : syntax error parse error
ERROR: 1 compilation errors. No code generated."

from the linker:

"Vertex and Fragment shader(s) were not successfully compiled before glLinkProgram() was called. Link failed."

so oviously is the shaders not the implementation.

Help...lol?

Cheers
Alex

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That character only appears in your comments, so I guess it's trying to parse those for some reason... maybe there's a problem with your readFile() routine. Before you go changing it, try testing with simpler shaders, like these ones:

vert shader:

void main()
{
gl_Position = ftransform();
}




frag shader:

void main()
{
gl_FragColor = vec4( 0.2, 0.7, 0.2, 1.0 );
}

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well even with the basic shader:

frag:
void main(void)
{
gl_FragColor = vec4( 0.4, 0.0, 0.9, 1.0 );
}

vert:
void main(void)
{
gl_Position = ftransform();
}

im getting a similar error but with a different number before the '<':
"Vertex shader failed to compile with the following errors:
ERROR: 0:4: '<' : syntax error parse error
ERROR: 1 compilation errors. No code generated."


my read file code is here:

char* readFile(char *fileName){
int fileLength;
char *buffer;

ifstream file;
file.open(fileName, std::ios::binary);

if(!file.is_open())
return NULL;

//Seek to end of file to find length
file.seekg(0, std::ios::end);
fileLength = file.tellg();
//Seek back to begin
file.seekg(0, std::ios::beg);

//Allocate memory to buffer now know length
buffer = new char[fileLength];

//read file into buffer
file.read(buffer, fileLength);

//close the file and return buffer
file.close();
return buffer;
}

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After looking at what was returned its got crap at the end of it:

‡readFile returned 0x00565b78
"void main(void)
{
gl_FragColor = vec4( 0.4, 0.0, 0.9, 1.0 );
}
ýýýý««««««««îþîþîþ"


what the heck is going on?

cheers
Alex

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nope makes no difference, and I dont think it should anyway.

Is the fileLength assignment correct, thats what could be giving the crap because its looking further than what the file could give

yeah in a basic vertex shader the char count is 48, but the value returned to fileLength is 53...hmmm
-Alex

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lightbringer you were so right.

It was that it didnt know the length and the file wasnt null terminated.

Replacing the NULL in glShaderSourceARB() with the value (pointer to) worked!!!


Thankyou so very much lightbringer!

Cheers
Alex

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Quote:
Original post by appleGuy
After looking at what was returned its got crap at the end of it:

‡readFile returned 0x00565b78
"void main(void)
{
gl_FragColor = vec4( 0.4, 0.0, 0.9, 1.0 );
}
ýýýý««««««««îþîþîþ"


what the heck is going on?

cheers
Alex



:) Listen grasshopper!

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