Questions tagged [opengl]

OpenGL (Open Graphics Library) is a graphics standard and API which is platform-independent and available for desktop, workstation and mobile devices. It is designed to provide hardware-accelerated rendering, and hence gives greatly improved performance over traditional software rendering. OpenGL is used for applications like CAD software and computer games. The OpenGL standard, as well as OpenGL ES, is controlled by the Khronos group.

Filter by
Sorted by
Tagged with
1 vote
1 answer
61 views

Using original vertices coordinates after clipping

Clipping is down in homogeneous clip space, therefore after multiplying the vertices by the model-view matrix. But as we do clipping in clip space, the position of the new vertices that we interpolate ...
user avatar
0 votes
1 answer
175 views

Get binding point of sampler/image in shader

I have an image and a sampler declared in a shader as follow layout(binding = 5) uniform isampler2D heightmap; layout(binding = 3) uniform writeonly uimage2D info; ...
user avatar
  • 139
0 votes
1 answer
81 views

OpenGL shader introspection/interface queries for images

I've been looking at Interface queries in order to prevent common mistakes that are time consuming to debug, such as forgetting to bind a buffer, binding the wrong resource type, etc. However, I wasn'...
user avatar
  • 139
1 vote
1 answer
117 views

Is it possible to send Texture Buffer to shader dynamically?

I want to send a series of integer to the geometry shader, while the data will be modified every frame. But when I try to retrive the sampleBuffer in geometry shader, it seems to keep output zero. Am ...
user avatar
1 vote
1 answer
228 views

Transfer the texture between two different sets of uv

Say I have a mesh with two sets of uvs. And I have a texture made for the first set of uvs. I would like to create a second texture that has the same relationship between its pixels and the second set ...
user avatar
2 votes
0 answers
200 views

How to retrieve data from Compute Shader to CPU?

I want to retrieve data that has created by the compute shader but have no clue how it works. After researching a few forums and articles on how it should work and this is what I came up with. Compute ...
user avatar
1 vote
1 answer
114 views

Does atomic functions on same memory location cause an performance issue?

is it worse to do for each invocation an atomicAdd on the same memory location than doing for each invocation an atomicAdd to a unique memory location? (I know, atomicAdd does not make sense when each ...
user avatar
  • 499
1 vote
0 answers
65 views

Conditionals and branching in shaders

This is a quite wide subject which implies a lot of topics such as the platform or the compiler, but I think that it could be useful for everyone to know more about this. A common mistake is to think ...
user avatar
  • 1,169
1 vote
1 answer
308 views

How are textures projected onto 3d models in texture painting applications

In most modeling software you can texture paint onto 3d models using so called stencil textures. They basically project a texture from the viewport view onto the model as seen for instance in the ...
user avatar
1 vote
1 answer
419 views

When unsetting a VAO, should you also unbind the associated VBOs?

I'm working with a js/wasm/c++ program that uses object oriented programming when updating the OpenGL state. There are corresponding c++ classes for VBOs (vertex buffer) and VAOs (vertex array). ...
user avatar
  • 113
1 vote
1 answer
185 views

OpenGL Framebuffer with multiple Depthbuffers inside

I am trying to put multiple depthbuffers into one Framebuffer. I want to use VR and render both eyes at the same time: that means, in the geometry stage I want to clone the incoming triangle to two ...
user avatar
  • 499
1 vote
2 answers
165 views

Why negate z when constructing projection matrix OpenGL

I constructed an orthographic projection matrix from this article on scratchpixel.com: ...
user avatar
0 votes
0 answers
131 views

Crystal ball rotation - I don't get why the code works

For context: I'm absolutely new to graphics programming and I've always had trouble getting the math. I had the task to write code for a crystal ball interface using OpenGL. There's an object in the ...
user avatar
1 vote
1 answer
598 views

How to scale signed distance field fonts properly?

I have a setup where I'm rendering a bunch of characters on a canvas with an SDF font. The users can zoom in to see the details of the smaller texts, but currently the smaller characters are quite ...
user avatar
  • 121
1 vote
0 answers
167 views

OpenGL/D3D11 offscreen render multiple buffering

Recently I've been looking at Vulkan, and one thing that I noticed is that the application is responsible for choosing which buffer to render to in the case of multiple buffering. This got me thinking:...
user avatar
2 votes
1 answer
228 views

Dynamic Ray-Triangle Intersection

I am working on a small simulation software which has a 3D Renderer that is using OpenGL. I render objects to the screen as triangle meshes. To be able to select the triangles on the screen, I have ...
user avatar
  • 23
2 votes
1 answer
138 views

Can the framebuffer in OpenGL jargon or its color buffer end up being the one and the same memory location as the one scanned by a display controller?

My understanding is: the 'framebuffer' in OpenGL is a collection of buffers: many (due to swapping or stereo rendering) color buffers, (only one?) z-buffer and (only one?) stencil buffer; each OpenGL ...
user avatar
2 votes
1 answer
123 views

Rendering moist/wet materials like human anatomies for surgical simulators

Real human anatomies look wet/ moist when operated. I am looking for some good methods for rendering anatomies in a virtual simulation, and hence I have done a literature survey on 'Rendering wet ...
user avatar
3 votes
1 answer
1k views

How to unproject cursor with orthographic projection

With perspective projection we can unproject screen space coordinates of the cursor to the near and far plane of the frustum and calculate the direction of the ray through the cursor. ...
user avatar
3 votes
1 answer
155 views

OpenGL task/mesh shader extension NV_mesh_shader not behaving as I expected

I am trying to get up to speed with the NV_mesh_shader extension from NVidia (on my RTX2080). Samples are rare, so I tried to come up with my own small sample. I am rendering a sphere (20 triangles) ...
user avatar
0 votes
1 answer
57 views

Force int array to compact memory

I have following structure which i use as an uniform buffer object. ...
user avatar
2 votes
1 answer
161 views

glutSolid* source code

I am trying to build a dedocohedron in OpenGL, and I know that there is a built-in function in GLUT for the purpose. I was wondering if there is a way to either see the sourcecode for those functions, ...
user avatar
  • 21
2 votes
1 answer
202 views

With vsync enabled where does the wait happen in OpenGL?

When having vsync enabled I'm imagining that OpenGL has an explicit wait function to try and keep the frame rate constant. If so where is this function implemented exactly? After running some tests <...
user avatar
3 votes
1 answer
519 views

Shader that transforms a mercator projection to equirectangular?

I am new in the OpenGL - GLSL and trying to make a shader that taking a mercator projection texture as a source and converting it to an equirectangular projection texture. Sample input: (1024x1024) ...
user avatar
0 votes
0 answers
19 views

Custom Create Maps in OpenGL

I am trying to create some procedurally created terrains for which i need to create noise maps. How do I create a texture of noise map in OpenGL and then pass that in my vertex shader as a heightMap? ...
user avatar
1 vote
0 answers
112 views

What is the projection matrix of reverse (Byzantine) perspective?

I would like to construct a projection matrix for reverse perspective. I'm using OpenGL and tried to modify concepts from this excelent tutorial. I came up with: $$ \begin{bmatrix} 2\frac{(near-M)}{...
user avatar
  • 11
1 vote
1 answer
326 views

OpenGL Render front and back faces with different shading for 3d modeller

I'm working on a simple 3d modeller and I would like to render the back facing triangles a bit darker, to easier differentiate between front and back faces. Like you can see in most modelling ...
user avatar
1 vote
1 answer
71 views

Do we have OpenGL shaders write out the intermediate *.o-esque file on first compile so that we can skip compiling them in run-time every single time?

Shaders get compiled during runtime every single time an app starts. I understand the reasoning for this is that there are so many GPU architectures out there that it does not make sense to ship pre-...
user avatar
  • 113
-1 votes
1 answer
121 views

When do people need to work directly with a graphical API (eg: Direct3D) instead of using already made software?

I had this doubt in my head for several months and have been unable to find an answer anywhere on internet. I know what OpenGL, DirectX, Vulkan, Metal, etc... are, I already know what they are used ...
user avatar
0 votes
0 answers
198 views

Generate hardcoded texture data to pass to shaders

I'm trying to manually create a color data to load as a texture with OpenGl for learning purposes. I created an unsigned char array consisting of 4 pixels with 3 ...
user avatar
1 vote
1 answer
346 views

Passing mat4 array to GLSL succeeding but producing GL_INVALID_OPERATION

I'm currently passing an array of bone positions to GLSL for a skeletal animation shader; the positions are passing successfully but producing a GL_INVALID_OPERATION error. I'm passing the matrices ...
user avatar
  • 21
0 votes
0 answers
270 views

Best practices fo OpenGL static buffer data : what is best for performance?

My question is : to allocate static mesh data (vertex/index buffers that never change), is it best : To go the "obvious" way : "1 mesh = 1 VBO", submitting data using glBufferData with GL_STATIC_DRAW ...
user avatar
  • 101
1 vote
2 answers
51 views

Older Api documentation

I am currently using a older IntelHd Gpu which supports Opengl3.1 (Glsl #version140). While trying to locate the relevant Api for this version ,the Khronos site only provides documentation for ...
user avatar
  • 121
1 vote
1 answer
198 views

Implicit conversion in glsl shaders

When specifying member values for a structure consisting of float values like vec3 or mat3, is it guaranteed that if an integer ...
user avatar
2 votes
1 answer
180 views

Vector graphics output from shader program

I’m fairly new to shader programs in general but I have a question concerning vector graphics. I understand that a pixel shader can generate the color information to draw some sort of geometry on ...
user avatar
0 votes
1 answer
339 views

How to read illum value from mtl file using Assimp library?

I am loading an OBJ file using the ASSIMP library. Following is the MTL file associated with the obj file. ...
user avatar
0 votes
0 answers
138 views

Specifying Fragment Shader Colors per Fragment (Instead of per Vertex)

I am learning about fragment shaders and have seen how by setting the colours of each vertex a triangle can be coloured via interpolation. However what if we want to use our own function to manually ...
user avatar
2 votes
1 answer
390 views

Texture loading- erratic working

I'm a noob to the OpenGL world and am picking up ideas through practice. I've been writing some code to build retro-arcade games recently and need to load textures to provide the graphic interface. I'...
user avatar
2 votes
2 answers
79 views

Techniques for making tesselated shapes appear smoother?

What are some common techniques for making the edges on a tesselated shape less apparent without increasing the amount of tesselation which is actually carried out? As an example, I followed along ...
user avatar
  • 153
1 vote
1 answer
252 views

glBindImageTexture returning INVALID_VALUE

I am currently having an issue with OpenGL as I am trying to load some vector information into a 3D texture. Currently, I am developing in OpenGL 4.6 which should support Image bindings. this my ...
user avatar
1 vote
2 answers
516 views

OpenGL Compute Shader Shared Maximum

I'm working on an OpenGL compute shader in which each work item results in a single number output I'll call x, as well as a struct output with more information, I'll call y. What I would like is a ...
user avatar
0 votes
1 answer
77 views

Keep constant number of visible circles in 3D animation

I have created a 3D animation with a perspective projection of white circles moving randomly in a fake 3D space projected on a 2D computer screen (GIF 1). Since I need to keep the same number of ...
user avatar
  • 113
0 votes
1 answer
75 views

Wrong reflection

Here is a youtube video showing my problem: youtube.com/watch?v=y8J7VhS2pkM I think I'm either doing the texture lookup on the reflection texture wrong, or the reflection or view matrix is somehow ...
user avatar
1 vote
0 answers
271 views

Sampling the depth component of a packed depth-stencil texture while rendering to its stencil component

I need to frequently perform depth testing for any given fragment at a different fragment location than the one rendered to. Since this isn't possible with normal builtin OpenGL depth testing ...
user avatar
0 votes
1 answer
507 views

Shader sampler2D uniforms instead of attributes

In the godot game engine (using opengl) it is not possible to define custom shader attributes. A workaround is creating a sampler2D texture uniform instead and use vertexId (or in fact UV since ...
user avatar
1 vote
0 answers
62 views

Implementing the derivation of the Smith Shadowing function for arbitrary distributions

I'm trying to implement the derivation of the masking function G_1 by Smith. The appendix of Walter et al 1, Hammons presentation 2 and this research paper 3 talk in detail about it and I feel as I do ...
user avatar
2 votes
1 answer
107 views

2D array texture with different filtering setting per texture?

Currently I have textures which need GL_NEAREST and some other need GL_LINEAR in the same texture2dArray. In the shader I perform a manual GL_NEAREST lookup via textureFetch(). To avoid this my ...
user avatar
1 vote
3 answers
497 views

How does graphics api like OpenGL determine which triangle is back face to cull?

When I was writing a software rasterizer for my university class, we did culling in eye coordinates. Essentially, we use cross product to get a normal from the 3 vertices (in eye coordinates), then ...
user avatar
3 votes
1 answer
369 views

Sampling the light vs. sampling the BRDF: difference in intensity

(possible duplicate) I'm trying to implement multiple importance sampling, as described in the PBRT book (no bouncing yet, I want to make MIS work first). What my problem is, that while the BRDF ...
user avatar
  • 151
2 votes
1 answer
71 views

Point light illuminating only half of a scene

A point light is illuminating only a half of a scene in my small 3D renderer. It happens on every scene I've tried (conference room, cornell box, etc). How do I go about debugging this? What could ...
user avatar

1 2 3
4
5
14