My question is can I use glDrawElements without using shader?
I generate my vbo like the following:
glGenBuffers(1, &vertexId_);
glBindBuffer(GL_ARRAY_BUFFER, vertexId_);
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex)*((tess.x + 1) * (tess.y + 1)), &pVertex[0].p.x, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid *) vOffset_);
glEnableVertexAttribArray(1);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid *) nOffset_);
glEnableVertexAttribArray(2);
glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid *) tOffset_);
glGenBuffers(1, &indexId_);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexId_);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(unsigned short)*idxCount_, &pIndices[0], GL_STATIC_DRAW);
glBindVertexArray(0);
So the question is can I just use glDrawElements without binding any shaders to draw? I'm using GL 4.0
There is not fixed pipeline in OpenGL 4.0, you need shaders to tell what to do with that data (vertexes) you are sending to the GPU.
There are many resources on how to start with shaders, for example this one: http://nehe.gamedev.net/article/glsl_an_introduction/25007/
EDIT: As others pointed below this is not entirely true. You can use a compatibility profile and use the fixed pipeline if it is supported. http://www.opengl.org/registry/doc/glspec40.compatibility.20100311.pdf
Related
I would excuse me if the title is not explicit
I have a little program which print some mesh on screen, the code I use to init and draw is the following :
(Here you have the init code)
glGenVertexArrays(1, &VAO);
glCreateBuffers(1, &VerticesVBO);
glCreateBuffers(1, &NormalVBO);
glCreateBuffers(1, &ColorVBO);
glBindVertexArray(VAO);
glNamedBufferStorage(VerticesVBO,vertexData.GetCount() * sizeof(float),&(vertexData[0]), GL_MAP_READ_BIT | GL_MAP_WRITE_BIT);
glNamedBufferStorage(NormalVBO,normalData.GetCount() * sizeof(float),&(normalData[0]), GL_MAP_READ_BIT | GL_MAP_WRITE_BIT);
glNamedBufferStorage(ColorVBO,colorData.GetCount() * sizeof(float),&(colorData[0]), GL_MAP_READ_BIT | GL_MAP_WRITE_BIT);
glBindBuffer(GL_ARRAY_BUFFER,VerticesVBO);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER,NormalVBO);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER,ColorVBO);
glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(2);
(and here come the rendering code)
glBindVertexArray(VAO);
if(showMesh && noLight.IsLinked() && light.IsLinked()){
OpenGLProgram& prog = (showLight)? light : noLight;
prog.Bind();
if(showLight)prog.SetVec3("viewPos",viewPosition.x,viewPosition.y,viewPosition.z);
prog.SetMat4("ViewMatrix", viewMatrix);
prog.SetMat4("ProjectionMatrix", projectionMatrix);
prog.SetMat4("ModelMatrix", transform.GetModelMatrice());
glDrawArrays(((prog.ContainTCS()) ? GL_PATCHES : GL_TRIANGLES), 0, SurfaceCount);
}
However since this OpenGL code is only compatible with OpenGL 4.5 I have made some change to ensure a compatibility with OpenGL 4.0 :
(Here is how I change the init code)
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VerticesVBO);
glGenBuffers(1, &NormalVBO);
glGenBuffers(1, &ColorVBO);
glBindVertexArray(VAO);
glBindBuffer(GL_ARRAY_BUFFER,VerticesVBO);
glBufferSubData(GL_ARRAY_BUFFER,0,vertexData.GetCount() * sizeof(float),&(vertexData[0]));
glBindBuffer(GL_ARRAY_BUFFER,NormalVBO);
glBufferSubData(GL_ARRAY_BUFFER,0,normalData.GetCount() * sizeof(float),&(normalData[0]));
glBindBuffer(GL_ARRAY_BUFFER,ColorVBO);
glBufferSubData(GL_ARRAY_BUFFER,0,colorData.GetCount() * sizeof(float),&(colorData[0]));
glBindBuffer(GL_ARRAY_BUFFER,VerticesVBO);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER,NormalVBO);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER,ColorVBO);
glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glEnableVertexAttribArray(2);
I have not changed the draw code. The probleme is, when using the OpenGL 4.5 init code, everythings is working, however when using the 4.0, code crash at first loop after the glDrawArrays(...) . I have no idea if the probleme is related to OpenGL but since it work perfectly with my 4.5 code ...
Someone can help me ? Thanks
You have to use glBufferData instead of glBufferSubData because it doesn't allocate space in gpu
I am trying to create two separate objects to be rendered at the same time, a cube and a sphere. The issue is once I add the code for the sphere, the cube
is missing some faces etc.
Here is my code:
glGenBuffers(1, &g_VBO);
glBindBuffer(GL_ARRAY_BUFFER, g_VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex)*g_numberOfVertices[0], g_pMeshVertices[0], GL_DYNAMIC_DRAW);
glGenBuffers(1, &g_IBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_IBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLint) * 3 * g_numberOfFaces[0], g_pMeshIndices[0], GL_DYNAMIC_DRAW);
glGenVertexArrays(1, &g_VAO);
glBindVertexArray(g_VAO);
glBindBuffer(GL_ARRAY_BUFFER, g_VBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_IBO);
glVertexAttribPointer(positionIndex, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), reinterpret_cast<void*>(offsetof(Vertex, position)));
glVertexAttribPointer(normalIndex, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), reinterpret_cast<void*>(offsetof(Vertex, normal)));
glEnableVertexAttribArray(positionIndex);
glEnableVertexAttribArray(normalIndex);
/////////////////////////////////////////ORN///////////////////////////////////////////////
glGenBuffers(1, &ornVBO);
glBindBuffer(GL_ARRAY_BUFFER, ornVBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertex)*g_numberOfVertices[1], g_pMeshVertices[1], GL_DYNAMIC_DRAW);
glGenBuffers(1, &ornIBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ornIBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLint) * 3 * g_numberOfFaces[1], g_pMeshIndices[1], GL_DYNAMIC_DRAW);
glGenVertexArrays(1, &ornVAO);
glBindVertexArray(ornVAO);
glBindBuffer(GL_ARRAY_BUFFER, ornVBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ornIBO);
glVertexAttribPointer(positionIndex, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), reinterpret_cast<void*>(offsetof(Vertex, position)));
glVertexAttribPointer(normalIndex, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), reinterpret_cast<void*>(offsetof(Vertex, normal)));
glEnableVertexAttribArray(positionIndex);
glEnableVertexAttribArray(normalIndex);
So it renders the sphere fine, but then all the cubes have missing triangle faces. I think I have narrowed it down to being an issue with the IBO side but I can't quite figure it out.
Here is the image: https://puu.sh/vLBSm/1617b5d996.png
Next to and behind the sphere and the cube are other cubes ignore those, they have the same issue but are purposefully there. I just can't work out how to display both properly. and Im sure it has something to do with this:
glGenBuffers(1, &ornIBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ornIBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLint) * 3 * g_numberOfFaces[1], g_pMeshIndices[1], GL_DYNAMIC_DRAW);
glGenVertexArrays(1, &ornVAO);
In the ORN code, you are overwritting the index buffer binding of the first VAO.
At this point:
glGenBuffers(1, &ornIBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ornIBO);
g_VAO is still active, so the index buffer binding is replaced by ornIBO. To solve that you should unbind g_VAO before starting the ORN code:
glBindVertexArray(g_VAO);
glBindBuffer(GL_ARRAY_BUFFER, g_VBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_IBO);
glVertexAttribPointer(positionIndex, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), reinterpret_cast<void*>(offsetof(Vertex, position)));
glVertexAttribPointer(normalIndex, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), reinterpret_cast<void*>(offsetof(Vertex, normal)));
glEnableVertexAttribArray(positionIndex);
glEnableVertexAttribArray(normalIndex);
//Unbind!!
glBindVertexArray(0);
With OpenGL shaders, I want to render two objects. Each is defined by a set of vertex positions and vertex indices for the triangles. When I make my buffers, I use the following code:
// Object 1 vertex positions
glBindBuffer(GL_ARRAY_BUFFER, object1_vertex_buffer);
glBufferData(GL_ARRAY_BUFFER, object1_vertices_size, object1_vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
// Object 1 vertex indices
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, object1_index_buffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, object1_indices_size, object1_indices, GL_STATIC_DRAW);
// Object 2 vertex positions
glBindBuffer(GL_ARRAY_BUFFER, object2_vertex_buffer);
glBufferData(GL_ARRAY_BUFFER, object2_vertices_size, object2_vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
// Object 2 vertex indices
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, object2_index_buffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, object2_indices_size, object2_indices, GL_STATIC_DRAW);
And then when I render my scene, I use the following code:
// Object 1
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, object1_index_buffer);
glDrawElements(GL_TRIANGLES, object1_num_indices, GL_UNSIGNED_INT, (void*)0);
// Object 2
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, object2_index_buffer);
glDrawElements(GL_TRIANGLES, object2_num_indices, GL_UNSIGNED_INT, (void*)0);
However, this results in only object 2 being drawn. What am I doing wrong?
If you have openGL 3.3+ you should use a VAO:
glBindVertexArray(vao1);
// Object 1 vertex positions
glBindBuffer(GL_ARRAY_BUFFER, object1_vertex_buffer);
glBufferData(GL_ARRAY_BUFFER, object1_vertices_size, object1_vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
// Object 1 vertex indices
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, object1_index_buffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, object1_indices_size, object1_indices, GL_STATIC_DRAW);
glBindVertexArray(vao2);
// Object 2 vertex positions
glBindBuffer(GL_ARRAY_BUFFER, object2_vertex_buffer);
glBufferData(GL_ARRAY_BUFFER, object2_vertices_size, object2_vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
// Object 2 vertex indices
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, object2_index_buffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, object2_indices_size, object2_indices, GL_STATIC_DRAW);
and then you only need to bind the right vao when drawing:
// Object 1
glBindVertexArray(vao1);
glDrawElements(GL_TRIANGLES, object1_num_indices, GL_UNSIGNED_INT, (void*)0);
// Object 2
glBindVertexArray(vao2);
glDrawElements(GL_TRIANGLES, object2_num_indices, GL_UNSIGNED_INT, (void*)0);
otherwise you will need to repeat the bind and glVertexAttribPointer calls between draws:
// Object 1
glBindBuffer(GL_ARRAY_BUFFER, object1_vertex_buffer);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, object1_index_buffer);
glDrawElements(GL_TRIANGLES, object1_num_indices, GL_UNSIGNED_INT, (void*)0);
// Object 2
glBindBuffer(GL_ARRAY_BUFFER, object2_vertex_buffer);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, object2_index_buffer);
glDrawElements(GL_TRIANGLES, object2_num_indices, GL_UNSIGNED_INT, (void*)0);
If this is all the code present, then there are several problems:
One has to enable vertex attributes by calling glEnableVertexAttribArray.
In the drawing code you are only rebinding the index buffer, but not the vertex buffer. Both, glBindBuffer(GL_ARRAY_BUFFER,... and glVertexAttribPointer change the current state, so you are overriding the first objects setting with the second ones. If you really want to work without VAOs, you'll have to bind the correct buffer before each draw call and update the glVertexAttribPointer
There is no VAO in use (VAOs are mandatory when working in Core profile but I would recommend using them also in compatibility mode)
How usually people draw several objects in OpenGL 3.3+?
I have 2 objects: a terrain and a sphere. For each object i have 2 arrays(of vertices and indices). I tried to set different VBO and IBO(like this):
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glEnableVertexAttribArray(2);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*)12);
glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*)20);
glBindBuffer(GL_ARRAY_BUFFER, m_VBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_IBO);
glDrawElements(GL_TRIANGLES, (size-1)*(size-1)*6, GL_UNSIGNED_INT, 0);
glBindBuffer(GL_ARRAY_BUFFER, m_VBOsphere);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_IBOsphere);
glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glDisableVertexAttribArray(2);
but looks like GPU calculates/draw everything only after closing of this function and I see only a sphere. So, what should I do?
It looks like you misunderstood the implications of binding a buffer, and the correct sequence of calls.
You expected that in this sequence, the draw call would get its vertices from the VBO with id m_VBO:
glBindBuffer(GL_ARRAY_BUFFER, m_VBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_IBO);
glDrawElements(GL_TRIANGLES, (size-1)*(size-1)*6, GL_UNSIGNED_INT, 0);
That's not the way it works. The current GL_ARRAY_BUFFER binding has absolutely no effect on the draw call.
You need to have the right VBO bound when glVertexAttribPointer() is called. Beyond the direct arguments that specify values for the setup of the corresponding attribute (format, stride, etc), this call also specifies that the currently bound VBO is used as the source for the attribute data.
Therefore, you need the glVertexAttribPointer() calls for each object, and call them after binding the corresponding VBO.
The call sequence is then:
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glEnableVertexAttribArray(2);
glBindBuffer(GL_ARRAY_BUFFER, m_VBO);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*)12);
glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*)20);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_IBO);
glDrawElements(GL_TRIANGLES, (size-1)*(size-1)*6, GL_UNSIGNED_INT, 0);
glBindBuffer(GL_ARRAY_BUFFER, m_VBOsphere);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*)12);
glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid*)20);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_IBOsphere);
glDrawElements(GL_TRIANGLES, 36, GL_UNSIGNED_INT, 0);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glDisableVertexAttribArray(2);
If you want to reduce the number of setup calls you need before each draw call, look up Vertex Array Objects (VAO).
In my project I'd like to edit given vertex position which is already in GPU.
Do I need to reload whole model or there is an function to change needed vertex.
This is how I pass mesh to GPU
void Mesh3v3n2t::PassToGPU()
{
glGenVertexArrays(1, &VaoId);
glBindVertexArray(VaoId);
glGenBuffers(1, &VboId);
glBindBuffer(GL_ARRAY_BUFFER, VboId);
glBufferData(GL_ARRAY_BUFFER, 32*vertices.size(),vertices.data(), GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 32, 0);
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 32, (void*)12);
glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 32, (void*)24);
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glEnableVertexAttribArray(2);
glGenBuffers(1, &IndexBufferId);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IndexBufferId);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, indices.size()*4, indices.data(), GL_STATIC_DRAW);
}
You can use glBufferSubData. You may want to rethink the GL_STATIC_DRAW usage hint if you're going to be doing this frequently, but it's not necessary.