How to transform a subset of a vertex in a vertex buffer?

Question

float linePos[6]={0.0f,5.0f,0.0f,0.0f,30.0f,0.0f};    
...

glGenBuffers(1, &buffer);
glBindBuffer(GL_ARRAY_BUFFER, buffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(float)*3*2, linePos, GL_STATIC_DRAW);

...
glUniformMatrix4fv(UniformColor.modelToWorldMatrixUnif, 1, GL_FALSE, glm::value_ptr(modelMatrix.Top()));
//this just transforms all vertices

glLineWidth(3);
glDrawArrays(GL_LINES,0,2);

I want to make some animation changing the position (ex.translate) of one end the line(linePos[0]) but not the other. How can I do that?

Answer 1

You can do that using glBufferSubData. In your case, with only 6 vertices, you can just replace the complete buffer using glBufferSubData. This prevents the reallocation that glBufferData does.

You shouldn't use GL_STATIC_DRAW if you change it often, thought.