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24

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 ...


21

If you're wondering about OpenGL coverage, a good place to start is the Steam Hardware Survey. http://store.steampowered.com/hwsurvey?platform=pc Unfortunately, it seems to be broken right now and it doesn't display any stats for videocards. :\ I've also read things like XP only supports up to a certain version DirectX 9 is comparable to OpenGL 2.1, ...


18

Is there a substantial overhead to allocating / deallocating VBOs (I mean the mere act of setting up a buffer)? Define "substantial." It is generally wise not to create them in the middle of frames; they should be set up during initialization or wherever. But this is true of most OpenGL objects, like textures, renderbuffers, or shaders. If I'm ...


15

The way OpenGL works, whenever you use non-VBO data, the driver has to make a copy of it - in practice creating a temporary VBO - since nothing stps you from modifying your user-space naked arrays between calls to OpenGL. There may be some driver-side trickery to make the temp allocation faster, but there's nothing you can do to avoid the copying. So yeah, ...


11

This is really a choice between performance and flexibility, but I'll list my opinions about it. One single VBO The positive sides are: Just one draw call to draw your scene. This increases performance. Although your application may require multiple draw calls, you can still have a single VBO and let the count and offset decide your drawing. Not ...


10

For some statistics about hardware compatibility you could look at Steam survey: http://store.steampowered.com/hwsurvey/ Although it lists DX10 and DX11, the hardware compatibility is the same as OpenGL 3 and OpenGL 4 respectively. Though note that OpenGL driver installation state on people is usually worse than DX. Windows XP doesn't support DX10 or DX11, ...


9

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 ...


8

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 ...


7

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 ...


6

If someone is interested in this problem, you can find solution on OpenGL forum. Basically, buffers can't be accessed by two threads or contexts simultaneously, neither for reading nor writing. Therefore, a locking mechanism like std::mutex is needed.


6

I think you want to change your attribute pointers, specifically the offsets you have listed. &vertices[0].position should be 0, &vertices[0].uv should be 24, &vertices[0].normal should be 12 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. ...


6

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 ...


5

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. ...


5

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 ...


5

Answer 1: Of course you can, without texturing capabilities vertex buffers would be next to useless. A VBO is just a chunk of binary data with the format you specify (position channel, normal channel, texcoord channel, etc.) that gets interpreted by a shader. When drawing an object, you are telling the GPU to fetch that batch of data and apply the ...


5

The last param to your texcoord pointer is an offset in bytes, not floats, so it's 12 (or 3 * sizeof (float) if you prefer).


5

and vertex arrays seem to be deprecated. Instead, if I understand correctly, Not quite. Vertex arrays are the foundation for vertex buffer objects. Only the storage moved from client to server side. What if I have a scene that has a lot of smaller geometry? Merge smaller geometry sets into larger VBOs. There's no need to have one VBO per geometry ...


5

The thing you seem to be missing is the concept of transforming objects. A mesh doesn't have a position in the world; it's just a collection of vertex data. When you render the mesh, you transform that vertex data from its default location to a place in the world. This is what all of that matrix stuff people use does; vertex positions can be transformed by ...


5

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 ...


4

I haven't found any literature about the modern way to do it. That's generally because the "modern way" to have character animation is to use skeletal bone weighing, not vertex blending. However, if you insist on doing vertex blend-based animation, you can. The simplest way is to simply send the two keyframes you want to blend between as the ...


4

You should have duplicate vertices on corners. That is a common practice. In the end you will have 2 vertice arrays, one for black and one for white cells. If my math serves me well - 64 vertices in each array.


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

Generally, to render extremely large meshes you want to subdivide the data into smaller, separate meshes and render each of those individually. This can be useful to alleviate memory pressure (although it won't always do so, in practice), but it also allows you to perform some culling on the large geometry to avoid bothering rendering huge chunks of ...


4

The vertex buffer object APIs were added to OpenGL's core API in version 1.5. At some point, they were available as extensions, such as ARB_vertex_buffer_object. Wikipedia has a good overview of the version history of OpenGL.


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

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 ...


3

Some observations: First, there's no error checking in the code. The obj loading seems incorrect. The vertices are copied into mesh.vertices (l. 212-214 in BlockRenderer). Using the DefaultCube, mesh.vertices contains 12*3 vertices, and the index buffer 36 ints. Problem seems that the indices reference into the original verts array and not into ...


3

For dynamic, animated objects reducing draw calls is not that easy as much data is required for each instance. You can pass multiple transformations at once as long as you have constant registers left and use GL_ARB_draw_instanced to let opengl draw the VBO multiple times with an automatically incrementing instanceId that you can use to access the ...


3

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 ...



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