Hot answers tagged

27

With modern OpenGL's VBO's are the way to go, fixed function stuff (including glBegin/glEnd and the stuff in between) has been deprecated since 3.0 and removed since 3.1. With the OpenGL Core Profile, OpenGL ES 2.0+ and WebGL you don't even have access to the old stuff. Some people think learning the old stuff first is better because it's a bit easier, but ...


18

VAOs do not contain "glBindBuffer" state, with the exception of GL_ELEMENT_ARRAY_BUFFER's binding state. What you're not understanding is that glBindBuffer(GL_ARRAY_BUFFER) doesn't do anything. Well, it doesn't do anything as far as rendering is concerned. Try it; right before calling glDraw*, call glBindBuffer(GL_ARRAY_BUFFER, 0); your rendering will work ...


10

What you're looking for is instancing. You simply call glDrawArraysInstanced​ or glDrawElementsInstanced​, passing the number of instances that you want. There are two ways to then determine per-instance data: The gl_InstanceID vertex shader input tells you which instance is currently being processed. Your vertex shader can have an internal mechanism for ...


9

This is a complex question with a lot of small details that really matter, the performance will vary based on platform and application. So you should profile for possible bottlenecks before investing in optimizations. That said, firstly, I assume you should reduce uploads and updates as much as you can, for example use instancing. Secondly, note that GPUs ...


8

I think you want to change your attribute pointers, specifically the offsets you have listed. &vertices[0].position should be 0, &vertices[0].normal should be 12, &vertices[0].uv should be 24, and so on. Since getting the address of a struct member gives you the absolute address instead of the address relative to the beginning of the struct. ...


8

You cannot use separate index buffers in the way you intend to. But since you are writing your own importer, you can very well reorganise the in-memory data so that both the position and texture information are indexed the same way. This possibly means duplicating information in the process, but that cost must be put in regard to the overall bandwidth gain ...


8

For small data like this, you want glBufferSubData, sweet and simple :) Later on you probably should look into glMapBuffer though, as it is how you work with data larger than a few kilobytes quickly.


7

In this code, normals are not indexed. They most certainly are. They merely share the same index as the position. What you want is not generally possible. All vertex attributes must use the same index. You must convert your multi-indexed data to single-indices per vertex. There are techniques you could use to avoid this, but they generally require semi-...


7

This answer is more or less in flux, due to the recent advent of this. In general, what you want to avoid is calling glVertexAttribPointer wherever possible. There are several tools for this; the biggest is the use of BaseVertex indexed rendering. This allows you to put multiple models into the same buffers, with the same vertex formats. Then, you draw each ...


7

With VBOs you generally have two major advantages. Advantage 1 relates to fully static data and comes from being able to keep your vertex data in memory that is more optimal for the GPU. Advantage 2 relates to dynamic data and comes from being able to specify your vertex data at any point in time prior to using it for rendering, which can pipeline better. ...


7

Basically, it's not easy to get the vertex data back from the video card once it's there. Keeping the vertex data available to the CPU allows for a number of things, here are a few: As melak47 suggests, it allows the developer to free up video memory by freeing a VBO, while being able to quickly replace the data without needing to read from disk again. It ...


6

I would expect glDrawArrays to be fastest on both the GPU and CPU for this scenario, primarily because you're saving the GPU memory bandwidth otherwise used for fetching the index data and the CPU cost of managing the index buffer. I do not expect glDrawRangeElements to be any faster than glDrawElements - in fact, I would expect it to be slightly slower. ...


5

The VAO stores the glVertexAttribPointer state. Changing the VAO does not affect the current glBindBuffer, nor does changing the glBindBuffer affect the VAO. Only the glVertexAttribPointer call affects the VAO, by recording the buffer in use at the call. So the answer to your question is no. One option if you want to reduce the number of objects is to put ...


5

I can't say to be expert of this subject, and in my game project(s) I have concentrated more on 3D side, so my 2D side is pretty simple generally using things made for 3D side; and obviously, my perspective is at gaming side, so my 2D graphics is more about blitting sprites than geometry. From that perspective, 1) Squares and rectangles are pretty easy. I ...


5

Your main question seems to be: What would be the best way to draw frequently (really frequently, basically every frame) changing geometry with modern OpenGL? In most ways, there's no big difference between 2d and 3d OpenGL. The graphics pipeline has that one extra coordinate, Z, which won't be used as much in 2d, but that's about it. There's a few ways ...


4

You are currently putting the position data into one VBO (vertexBuffer[0]) and the color data into another one (vertexBuffer[1]). But when drawing you bind both buffers one after the other, so the second binding will just override the previous one. Then you set the pointers as if both attributes were in the same buffer. This is slightly messed up. The gl......


4

If this is for desktop OpenGL or OpenGL|ES 3 and you're doing a common 2D sprite-style engine, you won't have a lot of repeat geometry. Everything is quads. You only need a single vertex buffer and index buffer (describing a quad). Use instancing to put all the transformation matrices for your scene objects into a single buffer and then draw that single ...


4

As has been stated many, many times before, glVertexAttribPointer takes the buffer object that was bound to GL_ARRAY_BUFFER at the time the function is called. Changing the GL_ARRAY_BUFFER binding will have no effect on rendering unless you make the glVertexAttribPointer calls again.


4

I pasted together a running version here (just for demo purposes, I hacked around your existing names and structures) Like I said, your indices were wrong. How you got your MVP matrix I don't know, but it still looks wrong, maybe you transposed it or printed it out transposed. Also, the way you used glBindAttribLocation() and glBindFragDataLocation() is ...


4

I put together a greedy meshing implementation for voxel data which includes various attributes (https://www.youtube.com/watch?v=0OZxZZCea8I). I understand you're looking to merge voxel faces even when they aren't the same voxel type - but it would seem that the only way to do that is to send the set of voxel types represented by the quad into the shader ...


4

My hunch is that it's the creation of the VBO each time. If you data is truly dynamic you could try not using the VBO at all and just passing interleavedBuffer to glVertexPointer, etc. That leaves what happens in the hands of the driver. Probably it will copy your data into a buffer somewhere internally, but in a more optimal way since it has more ...


4

Yes, your UVs are being mapped to the vertices, not to the indices -- that's the way that vertex buffers work. Your vertex isn't just the position -- it's also the color, normal, texture coordinate, and any other attributes which you've attached to it. In a case like the one here, you'll actually need a separate copy of each vertex for each face, because ...


4

If you don't do any optimization you are rendering up to ~half a billion vertices, you can: Remove faces/vertices where blocks touch, and don't issue draw calls for chunks that lay outside of the FOV. Beyond that you can do more advanced vismap approaches, and merge faces when possible. If you still think there is something wrong, i suggest you edit your ...


4

There is a lot of misinformation floating around here. Buffer Objects were introduced into core in OpenGL 1.5. They existed in extension form as far back as OpenGL 1.4. Vertex Buffer Objects are basically an evolution of ATi's original Vertex Array Object extension. That extension has the unfortunate honor of sharing its name with a completely different ...


4

Yes, doing several draw calls is slower than one. This is why state changes are expensive. There are techniques (like instancing) that fight this, but they're still more expensive than simply doing a single draw call. To combine several VBOs into one, they must have the same state (i.e, same shader, same textures, etc), and they must be static (i.e, not ...


4

There are many cleaver ways of drawing 2D geometry with modern shader-centric OpenGL. The method that I usually choose and find the most straightforward is with simple batching. On startup, create a system-side buffer of 2D vertexes (the batch). This buffer can have a fixed size or can be resizable (like a std::vector in C++). Also create a VBO with the ...


4

Yes, sending your mesh data to the GL every time you render it would be very wasteful. You should only be doing that if your data has changed from one frame to another (e.g. you are computing animations in the CPU). Otherwise, you shouldn't have to re-submit data if the model/mesh was not changed. Apparently, the problem with your program is that you are ...


Only top voted, non community-wiki answers of a minimum length are eligible