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!
By the way, have been working on this for 3 days.
in texture class:
constructor:
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);
}
Texture binding function:
void Texture::Bind(){
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, m_texture);
}
In my main.cpp:
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;
uploade triangle 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 in my 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
}
I found one way to make it work.
I copy every lines in Texture constructor and paste it to draw(), instead calling texture.Bind(). Looks like I make a texture just before it's ready to draw a geometry and this way is working.
But I still have to know why it happens like that. For coding style, I still have to put my code in Texture class. Would you mind to provide a solution that what happened before?
