Related
The documentation states
glBufferData creates a new data store for the buffer object currently
bound to target. Any pre-existing data store is deleted. The new data
store is created with the specified size in bytes and usage.
So I code
// allocate storage in GPU and copy data
glBufferData(
GL_ARRAY_BUFFER,
myData.VertexCount()*sizeof(GL_FLOAT),
myData.Vertex(),
GL_STREAM_DRAW);
...
glDrawArrays(
GL_TRIANGLES,
0,
myData.VertexCount() );
which is executed every time I need to refresh the scene.
From time to time the number of vertices changes greatly. When the number of vertices drops, the old data appears to be still present and a garbled rendering of the old data appears.
I can workaround this problem by creating the buffer index at the start of each refresh, then deleting it afterwards
// construct buffer index
GLuint vertexbuffer;
glGenBuffers(1, &vertexbuffer);
...
glDeleteBuffers(1,&vertexbuffer);
This is fine for the moment, but I would like to optmize things later, including reusing some of the vertices in the buffer without needing to make a fresh copy on each refresh.
The problem does not show up on all my machines. It looks like the machines with better graphics cards do not have the problem
For reference, here is the entire render code:
void Render()
{
// Background color
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT );
glUseProgram( myShaderID );
// Send our transformation to the currently bound shader,
// in the "MVP" uniform
glUniformMatrix4fv(myMatrixID, 1, GL_FALSE, &MVP[0][0]);
// enable vertices attribute buffer
glEnableVertexAttribArray(0);
// make current
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
// allocate storage in GPU and copy data
glBufferData(GL_ARRAY_BUFFER, myData.VertexCount()*sizeof(GL_FLOAT),
myData.Vertex(), GL_STREAM_DRAW);
// let shaders access buffer
glVertexAttribPointer(
0, // attribute. No particular reason for 0, but must match the layout in the shader.
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
// 2nd attribute buffer : colors
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
glBufferData(GL_ARRAY_BUFFER, myData.VertexCount()*sizeof(GL_FLOAT),
myData.Color(), GL_STREAM_DRAW);
glVertexAttribPointer(
1, // attribute. No particular reason for 1, but must match the layout in the shader.
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
glDrawArrays(GL_TRIANGLES, 0, myData.VertexCount() );
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glFlush();
myCanvas->SwapBuffers();
}
And here is the final, fixed production code. VertexCount() now returns actual count of vertices, not just the number of floats in the vertex vector.
/** Update GL display */
void Render()
{
// Background color
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT );
glUseProgram( myShaderID );
// Send our transformation to the currently bound shader,
// in the "MVP" uniform
glUniformMatrix4fv(
myMatrixID,
1,
GL_FALSE,
myCamera.ModelViewProjection() );
// enable vertices attribute buffer
glEnableVertexAttribArray(0);
// make current
glBindBuffer(GL_ARRAY_BUFFER, myVertexBufferID);
// allocate storage in GPU and copy data
glBufferData(
GL_ARRAY_BUFFER,
3 * myData.VertexCount()*sizeof(GL_FLOAT),
myData.Vertex(),
GL_STREAM_DRAW);
// let shaders access buffer
glVertexAttribPointer(
0, // attribute. No particular reason for 0, but must match the layout in the shader.
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
// 2nd attribute buffer : colors
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, myColorBufferID);
glBufferData(
GL_ARRAY_BUFFER,
3 * myData.VertexCount()*sizeof(GL_FLOAT),
myData.Color(),
GL_STREAM_DRAW);
glVertexAttribPointer(
1, // attribute. No particular reason for 1, but must match the layout in the shader.
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
glDrawArrays(GL_TRIANGLES, 0, myData.VertexCount() );
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glFlush();
myCanvas->SwapBuffers();
}
Your code is just not correct. You set up the vertex attrib pointer to read 3 GLfloats per vertex, and use myData.VertexCount() as the number of vertices in the draw call, but you upload only myData.VertexCount()*sizeof(GL_FLOAT) bytes to the VBO. As a result, you will read way past the end of the buffer, and results are just undefined behavior.
.
What is happening is that when you call glBufferData the GL driver gives you a position in its memory which likely is the same as the previous position. You think you can update part of the whole thing with glBufferData, but that's not true. The rest may coincide with old data or may not.
I think you'd better use glBufferSubData instead of glBufferData to update new data (or part of it) without deleting and recreating a data store.
You need deleting and recreating when newSize > oldSize.
I am trying to implement picking via following an opengl tutorial, I have a mesh with 6000 vertices and I wish to pick particular ones; I have chosen to do by redering uniquely coloured boxes at each vertex point, read the pixel on my mouse click at that point and that should return to me the ID of the closest vertex. The background is rendered as white so if I miss I get nothing.
However I have a problem, it only works most of the time; there are certain areas that if I click there I get white returned even though its clearly a vertex, and when rendering the colorized scene clearly has a redish box at the point I clicked.
Then there are white areas near the mesh, to the bottom left and at some random point away from it, returns me a hit.
I do not understand at all why this is happening, it should work.
void Display() {
Controls->setVector(indexed_vertices);
if (Controls->getPicking()) {
// Clear the screen in white
glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
for ( int i=0; i< indexed_vertices.size(); i++) {
// use shaders
glUseProgram(pickingProgramID);
// Get a handle for our "MVP" uniform
GLuint PickingMatrixID = glGetUniformLocation(pickingProgramID, "MVP");
glm::mat4 RotationMatrix = glm::toMat4(orientations);
glm::mat4 btTranslationMatrix = glm::translate(glm::mat4(1.0f), indexed_vertices[i]);
glm::mat4 myModelMatrix = ModelMatrix * Controls->getTranslationMatrix() * Controls->getRotationMatrix() * btTranslationMatrix;
MVP = ProjectionMatrix * ViewMatrix * myModelMatrix;
Controls->setCntrlsViewMatrix(ViewMatrix);
Controls->setCntrlsProjectionMatrix(ProjectionMatrix);
glUniformMatrix4fv(PickingMatrixID, 1, GL_FALSE, &MVP[0][0]);
// Convert "i", the integer mesh ID, into an RGB color
int r = (i & 0x000000FF) >> 0;
int g = (i & 0x0000FF00) >> 8;
int b = (i & 0x00FF0000) >> 16;
// OpenGL expects colors to be in [0,1], so divide by 255.
glUniform4f(pickingColorID, r/255.0f, g/255.0f, b/255.0f, 1.0f);
// 1rst attribute buffer : vertices
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, gvertexbuffer);
glVertexAttribPointer(
0, // attribute. No particular reason for 0, but must match the layout in the shader.
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
// Index buffer
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementbuffer);
// Draw the triangles !
glDrawElements(
GL_TRIANGLES, // mode
indices.size(), // count
GL_UNSIGNED_SHORT, // type
(void*)0 // element array buffer offset
);
// OpenGL expects colors to be in [0,1], so divide by 255.
}
glDisableVertexAttribArray(0);
glFlush();
glFinish();
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
// Read the pixel at the center of the screen.
// You can also use glfwGetMousePos().
// Ultra-mega-over slow too, even for 1 pixel,
// because the framebuffer is on the GPU.
unsigned char data[4];
glReadPixels(Controls->get_mx_cur(), Controls->get_my_cur(),1,1, GL_RGBA, GL_UNSIGNED_BYTE, data);
std::cout << "MX: " << Controls->get_mx_cur() << " MY: " << Controls->get_my_cur() << std::endl;
// Convert the color back to an integer ID
int pickedID =
data[0] +
data[1] * 256 +
data[2] * 256*256;
//std::cout << std::hex << pickedID << std::dec<<std::endl;
if (pickedID == 0x00ffffff) { // Full white, must be the background !
printf("Miss\n");
}
else {
std::cout << "mesh " << pickedID << std::endl;
}
// Uncomment these lines to see the picking shader in effect
glutSwapBuffers();
skip = true;
Controls->setPicking(false);
}
if (!skip) {
// White background
glClearColor(0.2f, 0.25f, 0.5f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
//glEnable(GL_CULL_FACE);
glUseProgram(ShaderIDs[0]);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, Texture);
glUniform1i(TextureID, 0);
glm::mat4 myModelMatrix = ModelMatrix * Controls->getTranslationMatrix() * Controls->getRotationMatrix();
MVP = ProjectionMatrix * ViewMatrix * myModelMatrix;
// The inverse transpose of the View Model Matrix will re-normalize the normals if there's
// been any scaling. Otherwise you don't need it.
glm::mat3 NormalMatrix = glm::mat3( glm::transpose(glm::inverse(ViewMatrix * myModelMatrix)));
Controls->setCntrlsViewMatrix(ViewMatrix);
Controls->setCntrlsProjectionMatrix(ProjectionMatrix);
glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
glUniformMatrix4fv(ViewMatrixID, 1, GL_FALSE, &ViewMatrix[0][0]);
glUniformMatrix4fv(ModelMatrixID, 1, GL_FALSE, &myModelMatrix[0][0]);
// Notice we're passing a 3 by 3 matrix here.
glUniformMatrix3fv(NormalMatrixID, 1, GL_FALSE, &NormalMatrix[0][0]);
glUniform3f(CameraID, cameraLoc.x, cameraLoc.y, cameraLoc.z);
glUniform3f(LightPosID, lightPosition.x, lightPosition.y, lightPosition.z);
// VBO buffer: vertices
// 1rst attribute buffer : vertices
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glVertexAttribPointer(
0, // attribute
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
// 2nd attribute buffer : UVs
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
glVertexAttribPointer(
1, // attribute
2, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
// 2rd attribute buffer : normals
glEnableVertexAttribArray(2);
glBindBuffer(GL_ARRAY_BUFFER, normalbuffer);
glVertexAttribPointer(
2, // attribute
3, // size
GL_FLOAT, // type
GL_FALSE, // normalized?
0, // stride
(void*)0 // array buffer offset
);
// Index buffer
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementbuffer);
if ( Controls->getRenderingMode() == 0 ) {
glDisable(GL_CULL_FACE);
glEnable(GL_DEPTH_TEST);
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
//glDisable(GL_POLYGON_OFFSET_FILL);
}
else if (Controls->getRenderingMode() == 1 ) {
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
glDisable(GL_CULL_FACE);
//glDisable(GL_POLYGON_OFFSET_FILL);
glUseProgram(ShaderIDs[1]);
glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
glUniformMatrix4fv(ViewMatrixID, 1, GL_FALSE, &ViewMatrix[0][0]);
glUniformMatrix4fv(ModelMatrixID, 1, GL_FALSE, &myModelMatrix[0][0]);
// Notice we're passing a 3 by 3 matrix here.
glUniformMatrix3fv(NormalMatrixID, 1, GL_FALSE, &NormalMatrix[0][0]);
glUniform3f(CameraID, cameraLoc.x, cameraLoc.y, cameraLoc.z);
glUniform3f(LightPosID, lightPosition.x, lightPosition.y, lightPosition.z);
}
else if (Controls->getRenderingMode() == 2 ) {
glUseProgram(ShaderIDs[1]);
//
glm::mat4 MyOffsetMatrix = glm::scale(glm::mat4(1.0f), glm::vec3(1.025,1.025,1.025));
MyOffsetMatrix = glm::mat4(1.0f);
glm::mat4 myModelMatrix2 = ModelMatrix * Controls->getTranslationMatrix() *
Controls->getRotationMatrix()*MyOffsetMatrix;
glm::mat3 NormalMatrix2 = glm::mat3( glm::transpose(glm::inverse(ViewMatrix *
myModelMatrix2)));
glm::mat4 MVP2 = ProjectionMatrix * ViewMatrix * myModelMatrix2;
glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP2[0][0]);
glUniformMatrix4fv(ViewMatrixID, 1, GL_FALSE, &ViewMatrix[0][0]);
glUniformMatrix4fv(ModelMatrixID, 1, GL_FALSE, &myModelMatrix2[0][0]);
// Notice we're passing a 3 by 3 matrix here.
glUniformMatrix3fv(NormalMatrixID, 1, GL_FALSE, &NormalMatrix2[0][0]);
glUniform3f(CameraID, cameraLoc.x, cameraLoc.y, cameraLoc.z);
glUniform3f(LightPosID, lightPosition.x, lightPosition.y, lightPosition.z);
// The rest is exactly the same as the first object
// 1rst attribute buffer : vertices
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
// 2nd attribute buffer : UVs
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, (void*)0);
// 3rd attribute buffer : normals
glEnableVertexAttribArray(2);
glBindBuffer(GL_ARRAY_BUFFER, normalbuffer);
glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
// Index buffer
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, elementbuffer);
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
glDisable(GL_CULL_FACE);
glEnable(GL_POLYGON_OFFSET_FILL);
// Draw the triangles !
glDrawElements(GL_TRIANGLES, indices.size(), GL_UNSIGNED_SHORT, (void*)0);
glEnable(GL_POLYGON_OFFSET_FILL);
glDisable(GL_CULL_FACE);
glEnable(GL_DEPTH_TEST);
glPolygonOffset(2.0f, 2.0f);
glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
//glDisable(GL_POLYGON_OFFSET_FILL);
glUseProgram(ShaderIDs[0]);
}
//glUseProgram(ShaderIDs[1]);
// Draw the triangles !
glDrawElements(
GL_TRIANGLES, // mode
indices.size(), // count
GL_UNSIGNED_SHORT, // type
(void*)0 // element array buffer offset
);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glDisableVertexAttribArray(2);
glutSwapBuffers();
}
}
The problem was two-fold: Crazy numbers returned is a result of improper multisampling enabled when I wanted specific colour values (how to have my cake and eat it might need a bit of work but right now I don't care), and secondly because glReadPixels() inverts the Y axis and needed to do Height - Current_Mouse_Position for the Y value.
Perhaps glPoints would be faster means of doing what I'm doing, I'll need to look into it.
Recently I started to learn OpenGL and I am beginning to learn the newer assets of it. For a while now I've been trying to work with VBOs, to draw a simple cube from a vertex point array. I am having trouble rendering it and understanding some of the arguments in the functions. It throws no errors but nothing is in my view.
float cubeVertPoints[72]; //An array containing the vertex points
Here is my VBO init
void loadBufferData()
{
glGenBuffers(1, &cubeVBO);
glBindBuffer(GL_ARRAY_BUFFER, cubeVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(cubeVertPoints[0])*3, &cubeVertPoints[0], GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(cubeVertPoints[0])*3, (void*)sizeof(GL_FLOAT));
}
Drawing
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-ratio, ratio, -1.f, 1.f, 1.f, -1.f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glBindBuffer(GL_ARRAY_BUFFER, cubeVBO);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(cubeVertPoints[0])*3, (void*)sizeof(GL_FLOAT));
glDrawArrays(GL_TRIANGLES, 0, 1);
glDisableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
You are not transferring all your data into the vertex buffer. The 2nd parameter of glBufferData takes the size of all of your vertex data in bytes. You should set it to sizeof(vertex) * vertex_count.
Also, calling glEnableVertexAttribArray and glVertexAttribPointer in loadBufferData is redundant. You should call them only in your rendering function.
Your second problem is with glVertexAttribPointer. You are not passing the correct offset to your vertex position data in your vertex data "structure". Since your vertices only consist of positions, this offset should be 0. If you would have positions and colors for each vertex, these offset could be 0 (for position) and sizeof(float) * 3 (for color, because you have 3 coordinates).
Finally, you only draw a single vertex. You should draw 72/3=24 if your cube has 24 vertices.
I think you can make your life easier by defining an actual structure for your vertices, like so:
struct Vertex
{
float position[3];
};
Then, you can compute offsets for each of your vertex positions, colors, etc, with (GLvoid*)(&((Vertex*)NULL)->position).
so I will need to edit this question. As stated in one of the comments, I changed to rendering method to use buffers. However, the geometry isn't being drawn correctly. If I use the same buffer and draw the vertices manually, it looks alright (without the texture though, something is messed up with it). I also tried constructing a buffer with just vertex information but that didn't help at all.
void ModelHandler::DrawModels(){
//go through each of the models
for(int i=0;i<Models3D.size();i++){
//glEnableClientState(GL_VERTEX_ARRAY);
//glVertexPointer(3, GL_FLOAT, 0, Models3D[i]->object.m_pVertice);
//now draw all the material groups with their vertices for the model
for(int j=0;j<Models3D[i]->object.mtlGroups.size();j++){
//Drawing the vertices manually from the buffer object seems to work
/*
for(int lj=0;lj<Models3D[i]->object.mtlGroups[j]->m_vecgroupVerticeIndex.size();lj++){
int mtlIndex2 = Models3D[i]->object.FindMaterial(Models3D[i]->object.mtlGroups[j]->mtlName);
bool tOn = false;
//check if there was a texture for this material
if(Models3D[i]->object.materials[mtlIndex2]->texturePresent){
glEnable(GL_TEXTURE_2D);
//glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
glBindTexture(GL_TEXTURE_2D, Models3D[i]->object.materials[mtlIndex2]->textureIDDiffuse);
tOn = true;
}
if(tOn){
glBegin (GL_QUADS);
glTexCoord2f (0.0, 0.0);
glVertex3f (0.0+5, 0.0, -2.0f);
glTexCoord2f (1.0, 0.0);
glVertex3f (1.4f+5, 0.0, -2.0f);
glTexCoord2f (1.0, 1.0);
glVertex3f (1.4f+5, -1.0, -2.0f);
glTexCoord2f (0.0, 1.0);
glVertex3f (0.0f+5, -1.0, -2.0f);
glEnd ();
}
glBegin(GL_TRIANGLES);
glColor3f(Models3D[i]->object.mtlGroups[j]->VBO[lj*3].colour[0],Models3D[i]->object.mtlGroups[j]->VBO[lj*3].colour[1],Models3D[i]->object.mtlGroups[j]->VBO[lj*3].colour[2]);
if(tOn){
glTexCoord2f (Models3D[i]->object.mtlGroups[j]->VBO[lj*3].tex[0], Models3D[i]->object.mtlGroups[j]->VBO[lj*3].tex[1]);
}
glVertex3f(Models3D[i]->object.mtlGroups[j]->VBO[lj*3].location[0], Models3D[i]->object.mtlGroups[j]->VBO[lj*3].location[1], Models3D[i]->object.mtlGroups[j]->VBO[lj*3].location[2]);
glColor3f(Models3D[i]->object.mtlGroups[j]->VBO[lj*3+1].colour[0],Models3D[i]->object.mtlGroups[j]->VBO[lj*3+1].colour[1],Models3D[i]->object.mtlGroups[j]->VBO[lj*3+1].colour[2]);
if(tOn){
glTexCoord2f (Models3D[i]->object.mtlGroups[j]->VBO[lj*3+1].tex[0], Models3D[i]->object.mtlGroups[j]->VBO[lj*3+1].tex[1]);
}
glVertex3f(Models3D[i]->object.mtlGroups[j]->VBO[lj*3+1].location[0], Models3D[i]->object.mtlGroups[j]->VBO[lj*3+1].location[1], Models3D[i]->object.mtlGroups[j]->VBO[lj*3+1].location[2]);
glColor3f(Models3D[i]->object.mtlGroups[j]->VBO[lj*3+2].colour[0],Models3D[i]->object.mtlGroups[j]->VBO[lj*3+2].colour[1],Models3D[i]->object.mtlGroups[j]->VBO[lj*3+2].colour[2]);
if(tOn){
glTexCoord2f (Models3D[i]->object.mtlGroups[j]->VBO[lj*3+2].tex[0], Models3D[i]->object.mtlGroups[j]->VBO[lj*3+2].tex[1]);
}
glVertex3f(Models3D[i]->object.mtlGroups[j]->VBO[lj*3+2].location[0], Models3D[i]->object.mtlGroups[j]->VBO[lj*3+2].location[1], Models3D[i]->object.mtlGroups[j]->VBO[lj*3+2].location[2]);
glEnd();
}
glDisable(GL_TEXTURE_2D);
*/
//####
glBindBuffer(GL_ARRAY_BUFFER, Models3D[i]->object.mtlGroups[j]->vboID);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, Models3D[i]->object.mtlGroups[j]->indexvboID);
/*
//this could also be used BUT if glDrawElements uses the indices (m_pgroupVerticeIndex), we will need to give the array with all the
//vertices to glVertexPointer. That array would be m_pVertice
//glVertexPointer(3, GL_FLOAT, 5, Models3D[i]->object.mtlGroups[j]->buffer);
*/
glEnableClientState(GL_COLOR_ARRAY);
glEnableClientState(GL_NORMAL_ARRAY);
glEnableClientState(GL_VERTEX_ARRAY);
//Get the material that belongs to this mtlGroup
int mtlIndex = Models3D[i]->object.FindMaterial(Models3D[i]->object.mtlGroups[j]->mtlName);
//check if there was a texture for this material
if(Models3D[i]->object.materials[mtlIndex]->texturePresent){
glEnable(GL_TEXTURE_2D);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
glBindTexture(GL_TEXTURE_2D, Models3D[i]->object.materials[mtlIndex]->textureIDDiffuse);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glTexCoordPointer(2, GL_FLOAT, sizeof(Vertex), BUFFER_OFFSET(12));
//glTexCoordPointer(2, GL_FLOAT, 5, Models3D[i]->object.mtlGroups[j]->buffer);
//glTexCoordPointer(2, GL_FLOAT, 0, Models3D[i]->object.m_pTexture);
}
// Resetup our pointers. This doesn't reinitialise any data, only how we walk through it
glNormalPointer(GL_FLOAT, sizeof(Vertex), BUFFER_OFFSET(20));
glColorPointer(3, GL_FLOAT, sizeof(Vertex), BUFFER_OFFSET(32));
glVertexPointer(3, GL_FLOAT, sizeof(Vertex), BUFFER_OFFSET(0));
glDrawElements(GL_TRIANGLES, Models3D[i]->object.mtlGroups[j]->m_vecgroupVerticeIndex.size()*3, GL_UNSIGNED_BYTE, BUFFER_OFFSET(0));
//glDrawElements(GL_TRIANGLES, Models3D[i]->object.mtlGroups[j]->m_vecgroupVerticeIndex.size()*3, GL_UNSIGNED_INT, Models3D[i]->object.mtlGroups[j]->m_pgroupVerticeIndex);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glDisableClientState(GL_COLOR_ARRAY);
glDisableClientState(GL_NORMAL_ARRAY);
glDisableClientState(GL_VERTEX_ARRAY);
glDisable(GL_TEXTURE_2D);
}
}
}
My buffer contains the vertices (array of Vertex structs):
struct Vertex {
GLfloat location[3];
GLfloat tex[2];
GLfloat normal[3];
GLfloat colour[3];
GLubyte padding[20]; //apparently to get 64 bytes -> improved performance
};
And here is how I initialize/generate buffers for each of the materials:
//This function was implemented based on the tutorial shown at
//http://sdickinson.com/wordpress/?p=122
void CObjLoader::GenerateVBO(){
for(int mj=0;mj<mtlGroups.size();mj++){
glGenBuffers(1, &mtlGroups[mj]->vboID);
//printf("bufferID: %d", mtlGroups[mj]->vboID);
glBindBuffer(GL_ARRAY_BUFFER, mtlGroups[mj]->vboID); // Bind the buffer (vertex array data)
// Allocate space. We could pass the mesh in here (where the NULL is), but it's actually faster to do it as a
// seperate step. We also define it as GL_STATIC_DRAW which means we set the data once, and never
// update it. This is not a strict rule code wise, but gives hints to the driver as to where to store the data
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex) * mtlGroups[mj]->m_vecgroupVerticeIndex.size()*3, NULL, GL_STATIC_DRAW);
glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(Vertex) * mtlGroups[mj]->m_vecgroupVerticeIndex.size()*3, mtlGroups[mj]->VBO); // Actually upload the data
// Set the pointers to our data. Except for the normal value (which always has a size of 3), we must pass
// the size of the individual component. ie. A vertex has 3 points (x, y, z), texture coordinates have 2 (u, v) etc.
// Basically the arguments are (ignore the first one for the normal pointer), Size (many components to
// read), Type (what data type is it), Stride (how far to move forward - in bytes - per vertex) and Offset
// (where in the buffer to start reading the data - in bytes)
// Make sure you put glVertexPointer at the end as there is a lot of work that goes on behind the scenes
// with it, and if it's set at the start, it has to do all that work for each gl*Pointer call, rather than once at
// the end.
glTexCoordPointer(2, GL_FLOAT, sizeof(Vertex), BUFFER_OFFSET(12));
glNormalPointer(GL_FLOAT, sizeof(Vertex), BUFFER_OFFSET(20));
glColorPointer(3, GL_FLOAT, sizeof(Vertex), BUFFER_OFFSET(32));
glVertexPointer(3, GL_FLOAT, sizeof(Vertex), BUFFER_OFFSET(0));
// When we get here, all the vertex data is effectively on the card
// Our Index Buffer, same as above, the variable needs to be accessible wherever we draw
glGenBuffers(1, &mtlGroups[mj]->indexvboID); // Generate buffer
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, mtlGroups[mj]->indexvboID); // Bind the element array buffer
// Upload the index array, this can be done the same way as above (with NULL as the data, then a
// glBufferSubData call, but doing it all at once for convenience)
glBufferData(GL_ELEMENT_ARRAY_BUFFER, mtlGroups[mj]->m_vecgroupVerticeIndex.size()*3*sizeof(GLubyte), mtlGroups[mj]->index, GL_STATIC_DRAW);
}
}
For the sake of simplicity, my index array looks like this: 0, 1, 2, 3, 4, 5, .... This means that my buffer contains some of the vertices twice. VBO and index have therefore the same length.
Maybe I am messing something up with the initialization?
So the error was the following (I will just copy my previous comments explaining the solution):
Ok, I've found the error. Apparently, I was using GLubyte for the indices and in my case, I have way more than 255 vertices. Changing to GLuint has resolved the issue. However, my texture still isn't drawn correctly onto the object. The object stays grey. But colors seem to work.
The .obj loader is yielding better results now and is ok with simpler models. I will do some further testing and in case of trouble, I will be back.
I have some code that loops through a set of objects and renders instances of those objects. The list of objects that needs to be rendered is stored as a std::map<MeshResource*, std::vector<MeshRendererer*>>, where an object of class MeshResource contains the vertices and indices with the actual data, and an object of classMeshRenderer defines the point in space the mesh is to be rendered at.
My rendering code is as follows:
glDisable(GL_BLEND);
glEnable(GL_CULL_FACE);
glDepthMask(GL_TRUE);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
for (std::map<MeshResource*, std::vector<MeshRenderer*> >::iterator it = renderables.begin(); it != renderables.end(); it++)
{
it->first->setupBeforeRendering();
cout << "<";
for (unsigned long i =0; i < it->second.size(); i++)
{
//Pass in an identity matrix to the vertex shader- used here only for debugging purposes; the real code correctly inputs any matrix.
uniformizeModelMatrix(Matrix4::IDENTITY);
/**
* StartHere fix rendering problem.
* Ruled out:
* Vertex buffers correctly.
* Index buffers correctly.
* Matrices correct?
*/
it->first->render();
}
it->first->cleanupAfterRendering();
}
geometryPassShader->disable();
glDepthMask(GL_FALSE);
glDisable(GL_CULL_FACE);
glDisable(GL_DEPTH_TEST);
The function in MeshResource that handles setting up the uniforms is as follows:
void MeshResource::setupBeforeRendering()
{
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glEnableVertexAttribArray(2);
glEnableVertexAttribArray(3);
glEnableVertexAttribArray(4);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, iboID);
glBindBuffer(GL_ARRAY_BUFFER, vboID);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0); // Vertex position
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 12); // Vertex normal
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 24); // UV layer 0
glVertexAttribPointer(3, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 32); // Vertex color
glVertexAttribPointer(4, 1, GL_UNSIGNED_SHORT, GL_FALSE, sizeof(Vertex), (const GLvoid*) 44); //Material index
}
The code that renders the object is this:
void MeshResource::render()
{
glDrawElements(GL_TRIANGLES, geometry->numIndices, GL_UNSIGNED_SHORT, 0);
}
And the code that cleans up is this:
void MeshResource::cleanupAfterRendering()
{
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glDisableVertexAttribArray(2);
glDisableVertexAttribArray(3);
glDisableVertexAttribArray(4);
}
The end result of this is that I get a black screen, although the end of my rendering pipeline after the rendering code (essentially just drawing axes and lines on the screen) works properly, so I'm fairly sure it's not an issue with the passing of uniforms. If, however, I change the code slightly so that the rendering code calls the setup immediately before rendering, like so:
void MeshResource::render()
{
setupBeforeRendering();
glDrawElements(GL_TRIANGLES, geometry->numIndices, GL_UNSIGNED_SHORT, 0);
}
The program works as desired. I don't want to have to do this, though, as my aim is to set up vertex, material, etc. data once per object type and then render each instance updating only the transformation information.
The uniformizeModelMatrix works as follows:
void RenderManager::uniformizeModelMatrix(Matrix4 matrix)
{
glBindBuffer(GL_UNIFORM_BUFFER, globalMatrixUBOID);
glBufferSubData(GL_UNIFORM_BUFFER, 0, sizeof(Matrix4), matrix.ptr());
glBindBuffer(GL_UNIFORM_BUFFER, 0);
}