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tre

OpenGL GLSL confusion

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Edit: Rewrote this first post, since noone were interested. I will be trying to get a grip of GLSL in another way instead. So, the first thing I've got to ask is how this texturing thing works. I've got shader designer 1.6 at it's working with these shaders:
// vertex shader
varying vec3 lightDir, normal;

void main(){
	normal = normalize(gl_NormalMatrix * gl_Normal);
	lightDir = normalize(vec3(gl_LightSource[0].position));

	gl_TexCoord[0] = gl_MultiTexCoord0;
	
	gl_Position = ftransform();
}


// fragment shader
varying vec3 lightDir, normal;
uniform sampler2D tex;

void main(){
	vec3 ct, cf;
	vec4 texel;
	float intensity, at, af;
	
	intensity = max(dot(lightDir, normalize(normal)), 0.0);
	
	cf = intensity * (gl_FrontMaterial.diffuse).rgb + gl_FrontMaterial.ambient.rgb;
	af = gl_FrontMaterial.diffuse.a;
	
	texel = texture2D(tex, gl_TexCoord[0].st);
	ct = texel.rgb;
	at = texel.a;
	
	gl_FragColor = vec4(ct * cf, at * af) * 2;
}

But it doesn't work in my OpenGL application. I create my texture like this:
glGenTextures(1, &texture[0].texID);
glBindTexture(GL_TEXTURE_2D, texture[0].texID);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, 3,texture[0].width, texture[0].height,
		0, GL_RGB, GL_UNSIGNED_BYTE, texture[0].imageData);

Then I bind it where I create my globe, like this (and this is where I also create the uniform)
glTranslatef(potX, potY, 0.0f);

glActiveTexture(GL_TEXTURE0);
int tex_loc = glGetUniformLocation(shader.id(), "tex");
glUniform1i(tex_loc, 0);
glBindTexture(GL_TEXTURE_2D, texture[0].texID);

glRotatef(-65.0f, 0, 1, 0);
glCallList(globe);

I have to say, that it doesn't really seem to matter if I initialize my shaders or not. No errors in my program. It compiles and shows my globe and the text and the star field behind it. The light is there (can't really tell if I'm using fragment lighting or not). I also do not see the big deal with shaders if I have to do what I've allways done and then create a shader to do it again? I've been using the Lighthouse2D and Swiftless tutorials to get to this point. Here's to hoping someone might want to give a hand :) Thanks, Marcus Axelsson [Edited by - tre on December 9, 2009 10:52:22 AM]

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Sorry for bumping this. But the OP has been totally edited and the thread has a new direction :)

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I don't see that you even activated the shader program, that might be you're problem: glUseProgramObjectARB(ShaderProgram);

Are you using some sort of class to manage shaders? The problem could be with something associated to that. Did you forget to instantiate/configure anything?

Also, create a 'varying vec2 TexCoord' instead. Then in the vertex shader assign it: TexCoord = gl_MultiTexCoord0.st, in the fragment shader you then access TexCoord instead. I can't remember off the top of my head the reason for it, but that's the recommended approach in the OpenGL spec. I'll have to look it up later and ref.

Oh, don't forget to disable the shader afterwards, or use a new one.
glUseProgramObjectARB(0);

[Edited by - npeqp on December 9, 2009 11:07:10 AM]

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Quote:
Original post by npeqp
I don't see that you even activated the shader program, that might be you're problem: glUseProgramObjectARB(ShaderProgram);

Are you using some sort of class to manage shaders? The problem could be with something associated to that. Did you forget to instantiate/configure anything?

Also, create a 'varying vec2 TexCoord' instead. Then in the vertex shader assign it: TexCoord = gl_MultiTexCoord0.st, in the fragment shader you then access TexCoord instead. I can't remember off the top of my head the reason for it, but that's the recommended approach in the OpenGL spec. I'll have to look it up later and ref.

Oh, don't forget to disable the shader afterwards, or use a new one.
glUseProgramObjectARB(0);


I use a shader class:
// snippet from "shaderProcessor.h"
class Shader {
public:
Shader();
Shader(const char *vsFile, const char *fsFile);
~Shader();

void init(const char *vsFile, const char *fsFile);

void bind();
void unbind();

unsigned int id();
private:
unsigned int shader_id;
unsigned int shader_vp;
unsigned int shader_fp;
};


Which I use to create my shaders.
// snippet from "shaderProcessor.cpp"
...
void Shader::init(const char *vsFile, const char *fsFile){
shader_vp = glCreateShader(GL_VERTEX_SHADER);
shader_fp = glCreateShader(GL_FRAGMENT_SHADER);

const char *vsText = textFileRead(vsFile);
const char *fsText = textFileRead(fsFile);

if(vsText == NULL || fsText == NULL){
// felmeddelande
return;
}

glShaderSource(shader_vp, 1, &vsText, 0);
glShaderSource(shader_fp, 1, &fsText, 0);

glCompileShader(shader_vp);
glCompileShader(shader_fp);

shader_id = glCreateProgram();
glAttachShader(shader_id, shader_fp);
glAttachShader(shader_id, shader_vp);
glLinkProgram(shader_id);
}
...

I use glUseProgram(0) to unbind shaders.

Then to initialize a shader I call shader.init("test.vert", "test.frag");.

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How do you set up the display list? (what calls are in it etc)
I would suggest starting with a minimal triangle and no lighting or anything, to make it easier to troubleshoot. I don't really understand what the problem is, is it just that the texture isn't showing, but the rest seems fine?
You should also check the result of glCompileShader, as it can fail if there's a typo or something in the shader code.

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Quote:
Original post by Erik Rufelt
How do you set up the display list? (what calls are in it etc)
I would suggest starting with a minimal triangle and no lighting or anything, to make it easier to troubleshoot. I don't really understand what the problem is, is it just that the texture isn't showing, but the rest seems fine?
You should also check the result of glCompileShader, as it can fail if there's a typo or something in the shader code.


The problem is that no matter what I do in the shader I'm not seeing any results. This row in the vertex shader: texCoord = gl_MultiTexCoord0.st * 0; should result in me not having a texture at all (as in Shader Designer 1.6). But the texture shows anyway.
This makes me wonder if I'm using any shaders at all.

This is how I set up my display lists
void buildLists(void){
Vertices vGlobe, vStars;
vGlobe.vPos("models/globe2.obj");
vStars.vPos("models/starmodel.obj");

int i = 0;

globe = glGenLists(1);
glNewList(globe, GL_COMPILE);
glBegin(GL_TRIANGLES);
glColor3f(0.0f, 1.0f, 0.0f);
for(i = 0; i < (int)vGlobe.f_v1.size(); i++){
glNormal3f(vGlobe.vNx[vGlobe.f_n1], vGlobe.vNy[vGlobe.f_n1], vGlobe.vNz[vGlobe.f_n1]);
glTexCoord3f(vGlobe.vTu[vGlobe.f_vt1], vGlobe.vTv[vGlobe.f_vt1], vGlobe.vTw[vGlobe.f_vt1]);
glVertex3f(vGlobe.vX[vGlobe.f_v1], vGlobe.vY[vGlobe.f_v1], vGlobe.vZ[vGlobe.f_v1]);

glNormal3f(vGlobe.vNx[vGlobe.f_n2], vGlobe.vNy[vGlobe.f_n2], vGlobe.vNz[vGlobe.f_n2]);
glTexCoord3f(vGlobe.vTu[vGlobe.f_vt2], vGlobe.vTv[vGlobe.f_vt2], vGlobe.vTw[vGlobe.f_vt2]);
glVertex3f(vGlobe.vX[vGlobe.f_v2], vGlobe.vY[vGlobe.f_v2], vGlobe.vZ[vGlobe.f_v2]);

glNormal3f(vGlobe.vNx[vGlobe.f_n3], vGlobe.vNy[vGlobe.f_n3], vGlobe.vNz[vGlobe.f_n3]);
glTexCoord3f(vGlobe.vTu[vGlobe.f_vt3], vGlobe.vTv[vGlobe.f_vt3], vGlobe.vTw[vGlobe.f_vt3]);
glVertex3f(vGlobe.vX[vGlobe.f_v3], vGlobe.vY[vGlobe.f_v3], vGlobe.vZ[vGlobe.f_v3]);
}
glEnd();
glEndList();

stars = glGenLists(1);
glNewList(stars, GL_COMPILE);
glBegin(GL_TRIANGLES);
for(i = 0; i < (int)vStars.f_v1.size(); i++){
glNormal3f(vStars.vNx[vStars.f_n1], vStars.vNy[vStars.f_n1], vStars.vNz[vStars.f_n1]);
glTexCoord3f(vStars.vTu[vStars.f_vt1], vStars.vTv[vStars.f_vt1], vStars.vTw[vStars.f_vt1]);
glVertex3f(vStars.vX[vStars.f_v1], vStars.vY[vStars.f_v1], vStars.vZ[vStars.f_v1]);

glNormal3f(vStars.vNx[vStars.f_n2], vStars.vNy[vStars.f_n2], vStars.vNz[vStars.f_n2]);
glTexCoord3f(vStars.vTu[vStars.f_vt2], vStars.vTv[vStars.f_vt2], vStars.vTw[vStars.f_vt2]);
glVertex3f(vStars.vX[vStars.f_v2], vStars.vY[vStars.f_v2], vStars.vZ[vStars.f_v2]);

glNormal3f(vStars.vNx[vStars.f_n3], vStars.vNy[vStars.f_n3], vStars.vNz[vStars.f_n3]);
glTexCoord3f(vStars.vTu[vStars.f_vt3], vStars.vTv[vStars.f_vt3], vStars.vTw[vStars.f_vt3]);
glVertex3f(vStars.vX[vStars.f_v3], vStars.vY[vStars.f_v3], vStars.vZ[vStars.f_v3]);
}
glEnd();
glEndList();
}






EDIT:
Allright, this was me showing how blind and stupid a person can be :)
I had forgot that I had created a folder for my shaders and forgot to add that to the shader initialization. Sorry about that.

Now my next step would be to add one texture to the dark side of the globe and one to the light side.

[Edited by - tre on December 9, 2009 12:17:57 PM]

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Step two (blending two textures, one in light one in dark) is allmost done. I've got it working in ShaderDesigner.
The "day" texture won't work.

Here's my globe function:
void drawGlobe(float size, int slices){
glTranslatef(potX, potY, 0.0f);

glBindTexture(GL_TEXTURE_2D, texture[0].texID);
glActiveTexture(GL_TEXTURE0);
int tex_loc0 = glGetUniformLocation(shader.id(), "TextureUnit0");
glUniform1i(tex_loc0, 0);

glBindTexture(GL_TEXTURE_2D, texture[2].texID);
glActiveTexture(GL_TEXTURE0);
int tex_loc1 = glGetUniformLocation(shader.id(), "TextureUnit1");
glUniform1i(tex_loc1, 1);


glRotatef(-65.0f, 0, 1, 0);
glCallList(globe);
}


And the shaders:
// vertex shader
varying vec3 lightDir, normal;
varying vec2 texCoord;

void main(){
normal = normalize(gl_NormalMatrix * gl_Normal);
lightDir = normalize(vec3(gl_LightSource[0].position));

gl_TexCoord[0] = gl_MultiTexCoord0;
gl_TexCoord[1] = gl_MultiTexCoord0;

gl_Position = ftransform();
}

// fragment shader
varying vec3 lightDir, normal;
varying vec2 texCoord;
uniform sampler2D TextureUnit0;
uniform sampler2D TextureUnit1;

void main(){
vec3 ct, cf, c;
vec4 texel;
float intensity, at, af, a;

intensity = max(dot(lightDir, normalize(normal)), 0.0);

cf = intensity * (gl_FrontMaterial.diffuse).rgb +
gl_FrontMaterial.ambient.rgb;;
af = gl_FrontMaterial.diffuse.a;

texel = texture2D(TextureUnit0, vec2(gl_TexCoord[0].st));

ct = texel.rgb;
at = texel.a;

c = cf * ct;
a = af * at;

float coef = smoothstep(1.0, 0.0, intensity);
c += coef * vec3(texture2D(TextureUnit1, vec2(gl_TexCoord[0].st)));

gl_FragColor = vec4(c, a);
}


I'm using the Lighthouse3D Multitexture tutorial for this. I think the problem is in my globe function. I can't seem to be able to push the correct texture unit to the shader.
The shaders work great in ShaderDesigner.

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Allright. Since I'm done with this now I'm doing this new post instead of editing.

The day texture and the night texture blends nice together. It might need some tweaking to get it looking just right.

I just used the Lighthouse tutorial (Link) for those who want the same effect.
The problem was getting my OpenGL program connecting and passing information correctly to the shader and also excluding/reactivating the right texture for the star map.

glActiveTexture(GL_TEXTURE1); to activate the second texture unit and then reverting back to glActiveTexture(GL_TEXTURE0); before doing the star map. And everything works.


My next step is to create some sort of atmosphere for the globe. I'm thinking about creating a new shader for this. Is this the right way to go?
At the moment I'm just activating the fragment light + globe lights shader in initialization and then unbinding/binding where it's needed. So this time I thought I'd create a new shader in the same way and do a second set of unbind/bind.
Or should I try to squeeze this new shader information into the current shader?

And how do I go about creating an atmosphere? Should I create a new sphere around the globe and add the shader to that?
I'm not trying to make a physically correct atmosphere, though. Just something that can fool the user to believe in an atmosphere.

Later I'd like to add animating clouds. Can I create some sort of animated perlin noise shader? What would the most efficient way to create clouds be?

Hoping for some guidiance here :)

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