I've been looking into how to make the bubble texture transparent but haven't found anything that would fit in my code. I have tried with glColor4f() but I might be putting it in the wrong place. I'm a total beginner in openGL and I've been given a basic code to which I need to add other objects in order to make a 2D scene. I also don't exactly know what every single line does.
These are the relevant pieces of code:
// Globals
GLuint locT; // location of "T" uniform variable in myShaderProgram
GLuint locT2;
// Textures
GLuint myBubblesTexture = 0;
// Shader program object for applying textures to our shapes
GLuint myShaderProgram;
// Vertex Buffer Object IDs for the ground texture object
GLuint bubblesPosVBO, bubblesColourVBO, bubblesTexCoordVBO, bubblesIndicesVBO;
// 1) Position Array - Store vertices as (x,y) pairs
static GLfloat bubblesVertices[] = {
-0.2f, -0.2f,
-0.2f, 0.2f,
0.2f, -0.2f,
0.2f, 0.2f
};
// 2) Colour Array - Store RGB values as unsigned bytes
static GLubyte bubblesColors[] = {
255, 0, 0, 255,
255, 255, 0, 255,
0, 255, 0, 255,
0, 255, 255, 255
};
// 3) Texture coordinate array (store uv coordinates as floating point values)
static float bubblesTextureCoords[] = {
0.0f, 1.0f,
0.0f, 0.0f,
1.0f, 1.0f,
1.0f, 0.0f
};
// 4) Index Array - Store indices to quad vertices - this determines the order the vertices are to be processed
static GLubyte bubblesVertexIndices[] = { 0, 1, 2, 3 };
void init(int argc, char* argv[]);
void setupBubblesTextureVBO(void);
void display(void);
void drawTexturedBubblesVBO(void);
int _tmain(int argc, char* argv[])
{
init(argc, argv);
glutMainLoop();
// Shut down COM
shutdownCOM();
return 0;
}
void init(int argc, char* argv[]) {
// Initialise COM so we can use Windows Imaging Component
initCOM();
// Initialise FreeGLUT
glutInit(&argc, argv);
glutInitContextVersion(3, 3);
glutInitContextProfile(GLUT_COMPATIBILITY_PROFILE);
glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE);
glutInitWindowSize(1200, 800);
glutInitWindowPosition(64, 64);
glutCreateWindow("Funky Fish");
// Register callback functions
glutDisplayFunc(display);
// Initialise GLEW library
GLenum err = glewInit();
// Setup colour to clear the window
glClearColor(0.2f, 0.2f, 0.8f, 0.0f);
glLineWidth(9.0f);
//Load textures
myBubblesTexture = fiLoadTextureA("bubbles.png");
//Shader setup
myShaderProgram = setupShaders(string("Shaders\\basic_vertex_shader.txt"), string("Shaders\\basic_fragment_shader.txt"));
// Get uniform location of "T" variable in shader program (we'll use this in the play function to give the uniform variable "T" a value)
locT = glGetUniformLocation(myShaderProgram, "T");
//Setup the bubbles using VBO
setupBubblesTextureVBO();
}
// our bubbles
void setupBubblesTextureVBO(void) {
// setup VBO for the quad object position data
glGenBuffers(1, &bubblesPosVBO);
glBindBuffer(GL_ARRAY_BUFFER, bubblesPosVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(bubblesVertices), bubblesVertices, GL_STATIC_DRAW);
// setup VBO for the quad object colour data
glGenBuffers(1, &bubblesColourVBO);
glBindBuffer(GL_ARRAY_BUFFER, bubblesColourVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(bubblesColors), bubblesColors, GL_STATIC_DRAW);
// setup VBO for the quad object texture coord data
glGenBuffers(1, &bubblesTexCoordVBO);
glBindBuffer(GL_ARRAY_BUFFER, bubblesTexCoordVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(bubblesTextureCoords), bubblesTextureCoords, GL_STATIC_DRAW);
// setup quad vertex index array
glGenBuffers(1, &bubblesIndicesVBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, bubblesIndicesVBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(bubblesVertexIndices), bubblesVertexIndices, GL_STATIC_DRAW);
}
void display(void) {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// draw our bubble
drawTexturedBubblesVBO();
glutSwapBuffers();
}
void drawTexturedBubblesVBO(void) {
glUseProgram(myShaderProgram);
glEnable(GL_TEXTURE_2D);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_BLEND);
// Move our bubble to the centre of the screen
GUMatrix4 T = GUMatrix4::translationMatrix(0.0f, 0.0f, 0.0f);
glUniformMatrix4fv(locT, 1, GL_FALSE, (GLfloat*)&T);
// Bind each vertex buffer and enable
// The data is still stored in the GPU but we need to set it up (which also includes validation of the VBOs behind-the-scenes)
// Bind texture
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, myBubblesTexture);
glUniform1i(glGetUniformLocation(myShaderProgram, "texture"), 0);
glEnable(GL_TEXTURE_2D);
glBindBuffer(GL_ARRAY_BUFFER, bubblesPosVBO);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, (const GLvoid*)0);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, bubblesColourVBO);
glVertexAttribPointer(1, 4, GL_UNSIGNED_BYTE, GL_TRUE, 0, (const GLvoid*)0);
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, bubblesTexCoordVBO);
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 0, (const GLvoid*)0);
glEnableVertexAttribArray(2);
// Bind the index buffer
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, bubblesIndicesVBO);
// Draw the object - same function call as used for vertex arrays but the last parameter is interpreted as an offset into the currently bound index buffer (set to 0 so we start drawing from the beginning of the buffer).
glDrawElements(GL_TRIANGLE_STRIP, 4, GL_UNSIGNED_BYTE, (GLvoid*)0);
// glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glDisable(GL_TEXTURE_2D);
// use to force disable our shaderprogram
// glUseProgram(0);
}
