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lalaphoon
06-30-2017, 09:17 AM
I'm trying to work on a texture mapping 2D to a triangle. But currently, I can only get a triangle that has a gradient colour without any texture on it. Which means, my texture function in glsl always return vec4(1,1,1,1) and my textCoords is working. How should I fix it? Any suggestions would be helpful to try!
Here is also the same question I posted on stack overflow:https://stackoverflow.com/questions/44830416/opengl-glsl-texture-function-always-returning-vec41-1-1-1-white-triangle

By the way, have been working on this for 4 days.

in texture class:
constructor:
(really new to here, might not have a good writing)

Texture::Texture(const std::string& fileName){

int width, height, numComponents;
//float* imageData = stbi_loadf(fileName.c_str(), &width, &height, &numComponents, 4);
unsigned char* imageData = stbi_load(fileName.c_str(), &width, &height, &numComponents, 4);
if(imageData == NULL){
cerr << "Texture loading failed for "<<fileName<< endl;
}

glGenTextures(1, &m_texture);
glBindTexture(GL_TEXTURE_2D, m_texture);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

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,GL_RGBA8,width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageData);


stbi_image_free(imageData);
}

and Binding function:

void Texture::Bind(){
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, m_texture);
}



in my main, it is used to create a shader, and connect shader to frag and vertex shader file. Then load all data to shader.


m_shader.generateProgramObject();
m_shader.attachVertexShader( getAssetFilePath("VertexShader.vs").c_str() );
m_shader.attachFragmentShader( getAssetFilePath("FragmentShader.fs").c_str() );
m_shader.link();

// texture created here
texture = Texture("Assets/bricks.jpg");


// enable vertex attribute indices
glGenVertexArrays(1, &m_vao_triangle);
glBindVertexArray(m_vao_triangle);

// Enable the attribute index location for "position" when rendering.
GLint positionAttribLocation = m_shader.getAttribLocation( "position" );
glEnableVertexAttribArray(positionAttribLocation);

GLint textCoordLocation = m_shader.getAttribLocation( "atextCoord" );
glEnableVertexAttribArray(textCoordLocation);


// Restore defaults
glBindVertexArray(0);


CHECK_GL_ERRORS;



...



//uploading vertex data to buffer

vec3 triangleVertices[] = {
// Construct equalaterial triangle
vec3(0.0f, 0.0f, 0.0f),
vec3(0.25f, 1.0f, 0.0),
vec3(0.5f, 0.0f, 0.0f)
};

vec2 textCoords[] = {
vec2(1.0f, 0.0f),
vec2(0.25f, 1.0f),
vec2(0.5f, 0.0f)};



// Generate a vertex buffer object to hold the triangle's vertex data.
glGenBuffers(1, &m_vbo_triangle);

//-- Upload triangle vertex data to the vertex buffer:
glBindBuffer(GL_ARRAY_BUFFER, m_vbo_triangle);
glBufferData(GL_ARRAY_BUFFER, sizeof(triangleVertices), triangleVertices,
GL_STATIC_DRAW);

glBindBuffer(GL_ARRAY_BUFFER, 0);
CHECK_GL_ERRORS;




//====generate buffer for holding texture coordinates====
glGenBuffers(1, &m_uv_triangle);
glBindBuffer(GL_ARRAY_BUFFER, m_uv_triangle);
glBufferData(GL_ARRAY_BUFFER, sizeof(textCoords), textCoords,
GL_STATIC_DRAW);

// Unbind the target GL_ARRAY_BUFFER, now that we are finished using it.
glBindBuffer(GL_ARRAY_BUFFER, 0);

CHECK_GL_ERRORS;





...





//Map buffer data to shader

glBindVertexArray(m_vao_triangle);

glBindBuffer(GL_ARRAY_BUFFER, m_vbo_triangle);
GLint positionAttribLocation = m_shader.getAttribLocation( "position" );
glVertexAttribPointer(positionAttribLocation, 3, GL_FLOAT, GL_FALSE, 0, nullptr);



glBindBuffer(GL_ARRAY_BUFFER, m_uv_triangle);
GLint textCoordLocation = m_shader.getAttribLocation( "atextCoord" );
glVertexAttribPointer(textCoordLocation,2, GL_FLOAT, GL_FALSE, 0, nullptr);


//-- Unbind target, and restore default values:
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);

CHECK_GL_ERRORS;






...





//UPLOAD UNIFORM TO SHADER
m_shader.enable();

...

GLint uniformLocation_diffuse = m_shader.getUniformLocation("diffuse");
glUniform1i(uniformLocation_diffuse, 0);
CHECK_GL_ERRORS;

m_shader.disable();

CHECK_GL_ERRORS;





...







//And draw function

glBindVertexArray(m_vao_triangle);
// below I tried, but didn't work
// glClear(GL_STENCIL_BUFFER_BIT);
// glEnable(GL_BLEND);
// glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
// glEnable(GL_DEPTH_TEST);

texture.Bind();
// do these below:
// glActiveTexture(GL_TEXTURE0);
// glBindTexture(GL_TEXTURE_2D, texture.m_texture);

m_shader.enable();

glDrawArrays(GL_TRIANGLES, 0, 3);


m_shader.disable();


// Restore defaults
glBindVertexArray(0);

CHECK_GL_ERRORS;



Here I will also attach my shaders vertex shader:




#version 330

in vec3 position;
in vec2 atextCoord;

uniform mat4 transform;
out vec2 textCoord;

void main() {
gl_Position = transform * vec4(position, 1.0);
textCoord = atextCoord;
}



And my fragment shader:



#version 330

uniform sampler2D diffuse;

out vec4 fragColor;
in vec2 textCoord;

void main() {

fragColor = vec4(texture(diffuse, textCoord).rgb,1.0) * vec4(textCoord,0.0,1.0);
// texture(...) shows vec4(1,1,1,1)
// radiant colour can only prove my textCoord is working
// fragColor = texture(diffuse, textCoord); <- only shows a default texture
}



Here is my running result:
2404


Here is my texture:
2405