CODEWITHSUNDEEP
openglcolorstexturesglslshader
David Szalai
David Szalai

Reputation: 2539

GLSL/OpenGL - Single color instead of the texture

I recently started learning GLSL, and now i have a problem with texturing. I've read all topics about it, i've found the same problem solid color problem, but there was a different problem that caused that. So, i have a simple quadrilateral(ground) and i simply want to render a grass texture on it. Shaders:

Fragment:

#version 330

uniform sampler2D color_texture;

in vec4 color;
out vec2 texCoord0;

void main() 
{
gl_FragColor = color+texture(color_texture,texCoord0.st);
}

Vertex:

#version 330
uniform mat4 projection_matrix;
uniform mat4 modelview_matrix;

in vec3 a_Vertex;
in vec3 a_Color;
in vec2 a_texCoord0;

out vec4 color;
out vec2 texCoord0;

void main() 
{            
texCoord0 = a_texCoord0;
gl_Position = (projection_matrix * modelview_matrix) * vec4(a_Vertex, 1.0);
color = vec4(a_Color,0.3);
}

My texture and primitive coords:

static GLint m_primcoords[12]=
{0,0,0, 
0,0,100,
100,0,100, 
100,0,0};
static GLfloat m_texcoords[8]=
{0.0f,0.0f,
0.0f,1.0f,
1.0f,1.0f,
1.0f,0.0f};

Buffers:

glBindBuffer(GL_ARRAY_BUFFER,vertexcBuffer);
glBufferData(GL_ARRAY_BUFFER,sizeof(GLint)*12,m_primcoords,GL_STATIC_DRAW);

glBindBuffer(GL_ARRAY_BUFFER,colorBuffer);
glBufferData(GL_ARRAY_BUFFER,sizeof(GLfloat)*12,m_colcoords,GL_STATIC_DRAW);

glBindBuffer(GL_ARRAY_BUFFER,textureBuffer);
glBufferData(GL_ARRAY_BUFFER,sizeof(GLfloat)*8,m_texcoords,GL_STATIC_DRAW);

and my rendering method:

GLfloat modelviewMatrix[16];
GLfloat projectionMatrix[16];

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();

cameraMove();

GLuint texturegrass = ploadtexture("grass.BMP");
glBindTexture(GL_TEXTURE_2D, texturegrass);

glGetFloatv(GL_MODELVIEW_MATRIX,modelviewMatrix);
glGetFloatv(GL_PROJECTION_MATRIX,projectionMatrix);

shaderProgram->sendUniform4x4("modelview_matrix",modelviewMatrix);
shaderProgram->sendUniform4x4("projection_matrix",projectionMatrix);

glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glEnableVertexAttribArray(2);

glActiveTexture(GL_TEXTURE0);
shaderProgram->sendUniform("color_texture",0);

glBindBuffer(GL_ARRAY_BUFFER,colorBuffer);
glVertexAttribPointer((GLint)1,3,GL_FLOAT,GL_FALSE,0,0);

glBindBuffer(GL_ARRAY_BUFFER,textureBuffer);
glVertexAttribPointer((GLint)2,2,GL_FLOAT,GL_FALSE,0,(GLvoid*)m_texcoords);

glBindBuffer(GL_ARRAY_BUFFER,vertexcBuffer);
glVertexAttribPointer((GLint)0,3,GL_INT,GL_FALSE,0,0);

glDrawArrays(GL_QUADS,0,12);

So, it looks like the code only reads 4 pixels from my texture(corners) and the output color will be outColor = ctopleft+ctopright+cbotleft+cbotright like this. I send more code if you want, but i think the problem lies behind these lines. I tried different coordinates, ordering, everything. I also read almost all topics about problems like this. Im using the beginning ogl game programming 2nd ed., but dont have cd, so i cant check if I'm coding well, cuz only parts of codes are in the book.

Upvotes: 2

Views: 5827

Answers (1)

Andon M. Coleman
Andon M. Coleman

Reputation: 43319

There are a couple of problems with your code.

  1. In the fragment shader, you have declared texCoord0 as out, it should be in in the fragment shader and out in the vertex shader, since it is passed from one to the other.

  2. You are binding your texture before you set the "active" texture unit. It defaults to GL_TEXTURE0, but this is still bad practice.

Upvotes: 1

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