opengl-4

问题 I'm having trouble using vertex buffer objects without using a vertex array object. My understanding was that VAOs are just encapsulating the state around VBOs. But shouldn't the VBOs be usable without a VAO? Here's a mini-example. With use_vao=true this works correctly (renders orange rect). With use_vao=false this renders nothing and generates a GL_INVALID_OPERATION error upon glDrawElements . // make sure the modern opengl headers are included before any others #include <OpenGL/gl3.h>

问题 I have a list of 3D vertices which I can easily render as a pointcloud by passing the whole list to my vertex shader, setting gl_Position = pos , then setting FragColor = vec4(1.0, 1.0, 1.0, 1.0) and use GL_POINTS in the drawing function. I would now like to render an actual cube at that vertex position, with the vertex being the center of the cube and some given width. How can I achieve this in the most easy and performant way? Looping through all vertices, loading a cube into a buffer and

问题 In the OpenGL Reference Pages, some functions are marked as using uniform locations, while other functions are marked as using uniform indices. Are these the same thing? Similarly for vertex attributes, some functions are marked as using vertex attribute indices, while other functions are marked as using vertex attribute locations. Are these the same? 回答1: In your first case, the location for an Uniform is different from the index used for glGetActiveUniform() . For glGetActiveUniform() case,

问题 I'm not sure which structure layout is most suited for my application: shared , packed , std140 , std430 . I'm not asking for an explanation of each, that information is easy to find, it's just hard to figure out the impact each will have on vendor compatibility/performance. If shared is the default, I'm suspecting that's a good starting point. From what I can gather, I have to query the alignment/offsets when using shared or packed , because it's implementation specific. What's the API for

问题 I was looking for ways to associate attributes with arbitrary groupings of verticies, at first instancing appeared to be the only way for me to accomplish this, but then I stumbled up this question and this answer states : However what is possible with newer versions of OpenGL is setting the rate at which a certain vertex attribute's buffer offset advances. Effectively this means that the data for a given vertex array gets duplicated to n vertices before the buffer offset for a attribute

问题 If I create a double-precision vertex buffer, for example: GLuint vertBuffer, spanBuffer, spanCount, patchSize, program; // already setup glUseProgram (program); glEnableClientState (GL_VERTEX_ARRAY); glBindBuffer (GL_ARRAY_BUFFER, vertBuffer); glVertexPointer (3, GL_DOUBLE, 0, 0); glPatchParameteri (GL_PATCH_VERTICES, patchSize); glBindBuffer (GL_ELEMENT_ARRAY_BUFFER, spanBuffer); glDrawElements (GL_PATCHES, spanCount * patchSize, GL_UNSIGNED_INT, 0); How do I access the double precision

问题 Originally using glDrawElementsInstancedBaseVertex to draw the scene meshes. All the meshes vertex attributes are being interleaved in a single buffer object. In total there are only 30 unique meshes. So I've been calling draw 30 times with instance counts, etc. but now I want to batch the draw calls into one using glMultiDrawElementsIndirect . Since I have no experience with this command function, I've been reading articles here and there to understand the implementation with little success.

问题 What are the diffences between "Shader Storage Buffer Objects" (SSBO) and Image load store operations When should one be used and not the other? They both can have atomic operations and I assume they are stored in the same type of memory. And regardless if they are stored in the same type of memory, do they have the same performance characteristics? edit: the original question was asking between SSBOs and Uniform buffer objects, it was meant to be between SSBO and Image load store. 回答1: The

问题 I've been working on a game engine and recently got to the point where I could easily create a Camera class to manage a view matrix (or allow an easy switch to another). I know conceptually what it must do, but where I'm having trouble is figuring out how to rotate about the local origin (for the view matrix, it would be the same as the translation matrix that is multiplied into a rotation matrix). I know that in direct mode, you would glTranslatef(x, y, z); //move back to origin glRotatef

问题 What I'm trying to do is load a texture into hardware from a single channel data array and use it's alpha channel to draw text onto an object. I am using opengl 4. If I try to do this using a 4 channel RGBA texture it works perfectly fine but for whatever reason when I try and load in a single channel only I get a garbled image and I can't figure out why. I create the texture by combing texture bitmap data for a series of glyphs with the following code into a single texture: int texture