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Change vertex colors in vertex buffer object


Change vertex colors in vertex buffer object

By : servoyguru
Date : November 20 2020, 01:01 AM
fixed the issue. Will look into that further Yes you can. Assuming you do have your data stored in a VBO, you could update select chunks of it by first binding said object and then using glBufferSubData. Take a look here. https://www.opengl.org/sdk/docs/man3/xhtml/glBufferSubData.xml
code :


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OpenGL Vertex buffer object, can I access the vertex data for other uses such as collision detection?

OpenGL Vertex buffer object, can I access the vertex data for other uses such as collision detection?


By : Catalyst
Date : March 29 2020, 07:55 AM
wish of those help Buffer objects, when used as sources for vertex data, exist for the benefit of rendering. Going backwards (reading the data back) is generally not advisable from a performance point of view.
The hint you give glBufferData has three access patterns: DRAW, READ, and COPY; these tell OpenGL how you intend to be getting/retrieving data from the buffer object directly. The hints do not govern how OpenGL should be reading/writing from/to it. These are just hints; the API doesn't enforce any particular behavior, but violating them may lead to poor performance.
How do I use a Vertex Buffer Object with a Vertex Array in OpenGL?

How do I use a Vertex Buffer Object with a Vertex Array in OpenGL?


By : benaf1
Date : March 29 2020, 07:55 AM
wish of those help
Am I right in my understanding that the glVertexPointer() tells the GPU where in the CPU it can fetch the vertices data and then the GPU copy it from this location in the CPU for each paintGL()?
code :
#define BUFFER_OFFSET(bytes) ((GLubyte*) NULL + (bytes)) 
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);

glBindBuffer(GL_ARRAY_BUFFER, vbufferid);
glVertexPointer(3, GL_FLOAT, 0, BUFFER_OFFSET(0));

glBindBuffer(GL_ARRAY_BUFFER, 0); // or put the colors into a VBO as well
glColorPointer(3, GL_FLOAT, 0,  colors);

glDrawElements(…
unsigned int vbufferid;
glGenBuffers(1, &vbufferid);  
glBindBuffer(GL_ARRAY_BUFFER, vbufferid); 

int vertexbufsize = (3)*numVertices*sizeof(float);
int colorbufsize = (3)*numVertices*sizeof(float);
glBufferData(GL_ARRAY_BUFFER, vertexbufsize + colorbufsize, NULL, GL_STATIC_DRAW); // data=NULL : initialize, but don't copy

glBufferSubData(GL_ARRAY_BUFFER, 0, vertexbufsize, vertices);
glBufferSubData(GL_ARRAY_BUFFER, vertexbufsize, colorbufsize, vertices);
#define BUFFER_OFFSET(bytes) ((GLubyte*) NULL + (bytes)) 
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);

glBindBuffer(GL_ARRAY_BUFFER, vbufferid);
glVertexPointer(3, GL_FLOAT, 0, BUFFER_OFFSET(0));
glColorPointer(3, GL_FLOAT, 0,  BUFFER_OFFSET(vertexbufsize));

glDrawElements(…
attaching a vertex buffer object to a vertex array object

attaching a vertex buffer object to a vertex array object


By : user2297213
Date : March 29 2020, 07:55 AM
like below fixes the issue I am trying to attach a vbo to a vao. However I only get it to work the "old" way: , Seems like I was missing
code :
glEnableVertexArrayAttrib(...);
glVertexArrayVertexBuffer(...);
glVertexArrayAttribFormat(...);
glVertexArrayAttribBinding(...);
Combining Vertex Array Object with Vertex Buffer & Index Buffer

Combining Vertex Array Object with Vertex Buffer & Index Buffer


By : T. Kendall
Date : March 29 2020, 07:55 AM
around this issue I am trying to combine a vertex array object with a vertex buffer & an index buffer using Qt. ,
code :
glDrawElements(GL_TRIANGLES, 3, GL_FLOAT, 0);
shaderProgram->enableAttributeArray(0);
shaderProgram->setAttributeBuffer(positionLocation, GL_FLOAT, 0, 3, 0);
Should I delete `Vertex Buffer Object` after binding it to `Vertex Array Objects`?

Should I delete `Vertex Buffer Object` after binding it to `Vertex Array Objects`?


By : Chris sivi
Date : March 29 2020, 07:55 AM
this will help Yes, as per OpenGL 4.5, it is legal to delete it after you unbind the VAO.
2.6.1.2 Name Deletion and Object Deletion
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