16
votes
Accepted
What is an index buffer and how is it related to vertex buffers?
Could someone ELI5 to me, what is an index buffer and how is it
related to vertex buffers
Your vertex buffer contains the X and Y coordinates of 5 vertices. They are:
...
- 443
9
votes
Accepted
How much should I rely on Geometry shaders in WebGL?
WebGL doesn't even currently support geometry shaders, so to directly answer the question: 100% of all users.
8
votes
Accepted
Help me find out what this texture mapping technique is called
What you see in the image called a UV map. That is, it is simply texture coordinates to be looked up encoded in a image. Same thing happens in all texture lookup in 3D there is a underlying sampler ...
- 8,397
7
votes
Can a scene graph be stored in the GPU?
Short answer: Yes, It can be done. But no one does so.
Long answer:
Scene graphs can be stored and processed on a GPU using OpenCL/WebCL. But it is not practical to do so. Updating scene graphs (a ...
- 651
7
votes
Accepted
WebGL Omnidirectional Shadow Mapping Issue
SOLUTION
After a couple of days I realized that I was computing my projection matrix using a FOV angle in degrees and It should be in radians. I made the conversion and now everything works great. ...
- 171
7
votes
Accepted
Why does substracting -1 in shader fail for a float data type?
Without seeing the error message I can't be sure but I think it's failing on the 1 being int instead of a float.
float inv_coord = v_coord - 1.0;
There is a ...
- 5,920
7
votes
Fading particles and transition
I made a visualization a little like yours years ago, and used a similar technique, because it's the natural approach to the problem. After I spent a few years writing drivers for modern GPUs, I ...
- 6,700
6
votes
What is an index buffer and how is it related to vertex buffers?
If you have a vertex buffer like this:
var vertices = [
0.0, 0.0, 0.0,
1.0, 0.0, 0.0,
0.0, 0.6, 0.0,
1.0, 0.6, 0.0,
0.5, 1.0, 0.0
]
And simply draw it ...
- 703
6
votes
Is it possible to create minimal glTF files with vertex and index buffers?
While creating a set of glTF models for a tutorial, I also intended to create THE minimal glTF file.
Update: The following referred to glTF 1.0/1.1. See below for an update of this example to glTF 2....
- 218
6
votes
What actually happens in frame buffer when an image or document is scrolled?
In the olden days of text-mode terminals, the "frame buffer" was a buffer of text, not an image. Scrolling worked in the way you described. The buffer was larger than would fit on the screen, and to "...
- 6,700
5
votes
Accepted
Can we use PhysX in WebGL?
PhysX is a C++ API and can thus not directly be integrated with the JavaScript-based WebGL.
Depending on your needs, you have the following options:
Use a JavaScript-based physics engine, mostly ...
- 2,293
5
votes
Accepted
How to use 32 bit Integers for Element Indices in WebGL 1.0?
Enabling the extension is as simple as:
var uints_for_indices = gl.getExtension("OES_element_index_uint");
if ...
- 5,920
4
votes
Is it possible to create minimal glTF files with vertex and index buffers?
You can put the data into a data uri to store the data inline in base64 format.
...
- 5,920
4
votes
Is it possible to store the plain buffer data in gltf files?
Embedding human readable data is not supported. However you can put the data into a data uri to store the data inline in base64 format.
...
- 5,920
4
votes
WebGL: Why are my textures black?
Okay, I figured it out. It has to do with the texture not loading before the first display function is called. The texture displays after a mouse or keyboard event. To remedy this, I added a timer to ...
- 71
4
votes
Accepted
Rendering same vertex-array in different modes
Your shaders are fine, the problem is topological, that is the way the vertices are connected to create triangles.
For cases 1 & 2: You cannot really draw a grid of points in this mode (...
- 2,312
4
votes
Accepted
Optimizing performance on hardware
Although you may be able to detect what hardware is available as a first approximation of a computer's capability, depending on this might not be useful since the same hardware may behave differently ...
4
votes
Accepted
Inverse matrix order of operation
Yes. If you're compounding operations to make a matrix, then the inverse matrix will be the compound of the inverse operations, in the reverse order. So if $C = AB$ then $C^{-1} = B^{-1}A^{-1}$
Think ...
- 2,372
4
votes
Accepted
Triangulation of vertices of an ellipsoid
If you sample the two parameters $\eta$ and $\omega$ with steps $d\eta$ and $d\omega$, then you'll get a grid of points $v_{ij} = f(i\;d\eta,j\;d\omega)$. Any four adjacent points will define a ...
- 881
4
votes
Accepted
Does WebGL 2 support linear depth texture sampling?
The spec says depth textures are not filterable.
3.8.13
...
Using the preceding definitions, a texture is complete unless any of the following conditions hold true:
The effective ...
- 214
3
votes
Only show opaque objects behind transparent objects
The simplest solution is to do three passes:
Render opaque meshes to a buffer (front-to-back, depth read/write on)
Render translucent meshes to another buffer (front-to-back, depth read/write on)
...
- 561
3
votes
Accepted
How to know when rendering is complete in WebGL?
You can utilize ARB_sync or in other words sync objects which have been core since 3.2.
From the point-of-view of OpenGL then right after issuing a specific command (you want to know whether has ...
- 251
3
votes
Need help reasoning about video oscillation >60hz
Yeah, that makes sense. Most flat panel monitors on the market have a 60Hz refresh rate! So you are not going to be able to flicker faster than 60Hz due to technical limitation.
Were you to do this ...
- 8,397
3
votes
Accepted
Emission of light from texture on WebGL
Presumably you are using a lighting system already, let's say Lambert shading for simplicity..
So we have a texture which is going to be illuminated by some light source. The following psuedo/shader ...
- 2,312
3
votes
Accepted
Is it possible to create minimal glTF files with vertex and index buffers?
After spending a hard time to understand the way how the binary buffers work in the gltf files I finally managed to generate a truely minimal gltf file. It's a single yellow triangle (demo).
I tried ...
- 703
3
votes
Accepted
What happens to float values written to UNSIGNED_BYTE texture?
Unsigned byte textures in a graphics API are usually "normalized"—the byte values are interpreted as ranging from 0.0 to 1.0, with a byte of 255 mapping to 1.0. So no, they aren't truly floating-point ...
- 24.8k
3
votes
Unable to render a Waveront model in WebGL2
The problem is with how wavefront files and OpenGL work with indices.
OpenGL
OpenGL allows you to have different buffers, allowing your vertex to have multiple attributes. However, for every vertex ...
- 1,595
3
votes
What is the technique to generate an oblique 3d cone?
The general equation for a upright cone with the tip at $Z=0$ is
$$ 0 = X^2 + Y^2 - Z^2$$
(Ignoring the points for which $Z>0$). If you consider slices for some constant $Z$ you get circles ...
- 246
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