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.

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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 ...
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1answer
231 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'...
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2answers
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 ...
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1answer
195 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 ...
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2answers
355 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 ...
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1answer
70 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 ...
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1answer
74 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 ...
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235 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 ...
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1answer
429 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 ...
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56 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 ...
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1answer
84 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 ...
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3answers
409 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 ...
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1answer
293 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 ...
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1answer
59 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 ...
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73 views

After making any 3D model using Opengl how to export it's data in .dae file?

I'm trying to make simple 3d modeling program in c++ with Opengl. So I don't know how to transfer/convert/export or save data of 3D model in .dae file. NOTE:- 3d model is made using Opengl ...
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1answer
157 views

Generating the end caps of a cylinder using triangle strips for use in a geometry shader

I know how to generate the walls of a cylinder with triangle strips and the caps with triangle fans, but since I am working inside a geometry shader, I can only output triangle strips, so I am kind of ...
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1answer
297 views

Implementing the example of Walter et al. (2007) paper

As the title suggests I'm trying to implement the last images of the "Microfacet Models for Refraction through Rough Surfaces" Paper by Walter et al. in OpenGL I "think" (I had to ...
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0answers
111 views

Why there are calculation differences in WebGL and OpenGL

I am currently implementing the Mandelbrot fractal on the GPU. I wrote two programs: the first in OpenGL (desktop C++ application) and the second in WebGL (static webpage). The two programs use almost ...
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133 views

Apply transformation to single vertices in OpenGL in order to deform mesh

I'm making a 2D cell simulation game. The mesh for my cell is basically just a manually-generated triangle fan that looks like this. I would like to reproduce the wobbling/vibration effect on the ...
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0answers
127 views

Projective Texture / Shadow Mapping -- Why is the perspective division performed in the fragment shader?

I've just worked my way through this OpenGL shadow mapping tutorial. While I understand the basic algorithm, one thing puzzles me: During the 2nd render pass all vertices are transformed into the clip ...
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1answer
247 views

Stumped on GLSL error C5041 (cannot located suitable resources to bind variable... possibly large array

I have an OpenGL based graphics engine coming along quite nicely, but I'm currently stumped on a problem that arose after adding a new vertex shader output array. The vertex shader is outputing the ...
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0answers
38 views

Optimizing texture fetches with higher mip levels

Let's say I have some shader program in DirectX or OpenGL rendering a full screen quad. And in a pixel/fragment shader I sample some huge textures at random texture coordinates. That is one same ...
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1answer
98 views

Strange VSync issues on a GTX 1060

I'm out of my wits. I've been working an a voxel game for the last couple of years, written in C# and OpenTK (=OpenGL backend) I've been struggling to achieve a stable frame rate and one of the major ...
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0answers
110 views

gBuffer view/eye space missing z (depth) value?

I need some help understanding whats happening to my view space. I have the following colour buffers coming out of my deffered renderer... My concern is with the view space buffer (third image), ...
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1answer
159 views

How to compute normal in quartic Walton-Meek's Gregory patch in tessellation shader?

I am programing a tessellation shader in OpenGL which computes the quartic Walton-Meek's Gregory patch. I am searching for a local G1 method with good shading/visual results. So I am trying this patch....
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2answers
51 views

Help with wireframe artifacts on mesh procedural UV texturing

My goal in my project is to render a procedural texture for a given mesh based on a predefined camera projection. The way I choose to accomplish it is by creating tex coords based on only the visible ...
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2answers
154 views

An idea for an implementation of continuous collision detection of circles [closed]

So I'm making a 2D pool game in OpenGL (you might've guessed as soon as I've mentioned collision of circles). I'm having a little trouble with collision detection. What I mean by that is that I have ...
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1answer
107 views

GLSL - increasing line spacing with y

I'm trying to force perspective into the horizon of a Shadertoy scene by drawing horizontal lines at decreasing distances as y grows to create an outrun-esque scene, but can't figure out which ...
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1answer
221 views

What are the type constants that the documentation for glGetProgramResourceiv() refers to?

Quoting the Khronos OpenGL documentation pages for the glGetProgramResourceiv() function: For the property GL_TYPE, a single integer identifying the type of an ...
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0answers
296 views

Why is glUniform1i() returning GL_INVALID_VALUE?

I have a sampler variable in a shader: uniform sampler2DArray tiles; Which I am trying to bind to a texture unit in GL: ...
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1answer
342 views

Double buffering always necessary?

Question from the graphics newbie: What I know by now is that "usually" double buffering is used: You calculate the content of frame x+1 while frame x is shown on the screen, if you want to achieve ...
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0answers
42 views

How combine multiple projections into a single pass?

We have a projector type display used in an automotive application, where a projector displays an application on the windshield. Because the projector would normally warp a flat image, we have to ...
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1answer
56 views

GLFW | What is a frame?

Here I was reading about buffers and found such text: When the entire frame has been rendered, the buffers need to be swapped with one another, so the back buffer becomes the front buffer and vice ...
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0answers
96 views

How to render multiple shaders per mesh

I've tried looking everywhere, but I just don't get it. How is multiple shaders assigned to a mesh if you can only bind a single shader in OpenGL? Assume I have a mesh with a texture shader and now I ...
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1answer
4k views

What's the difference between Clipping and Culling?

In a tutorial about OpenGL both words are mentioned, unfortunately without a good explanation. To find out, I have read this article three times, but I fear I'm a too common man... my understanding is ...
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1answer
115 views

In the rendering pipeline, in what coordinate space are vertices when they arrive at the primitive assembly stage?

Full disclaimer, this was a test question, but I couldn't find any information online. In my opinion, this depends on if the primitive assembly stage happens before or after perspective division. If ...
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1answer
131 views

About view matrix and frustum culling

I was trying to determine if an object (sphere) is inside a view frustum. My strategy was first to get the view matrix: ...
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1answer
367 views

Zero-copy texture reading from CPU memory

The Intel 740 AGP graphics card read textures directly from system RAM, using VRAM exclusively for depth buffers and the framebuffer. This has the effect of saving video RAM, and it could be ...
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2answers
2k views

Debugging tools for OpenGL on macOS

I am porting some code from Metal to OpenGL since we want to run our app on Windows too. Xcode is my preferred IDE, but the newer versions of Xcode do not support any OpenGL debugging. Question: What ...
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0answers
23 views

Confusion about glVertexAttribPointer and non-active attributes

When binding an attribute index using glVertexAttribPointer, what happens when a later bound program does not contain an attribute at said index? Is the behaviour undefined, or is the attribute ...
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1answer
106 views

Change of speed but no change of size after OpenGL Perspective Projection

I am new to OpenGL and I am trying to code un optic flow with dots appearing from the background and moving towards the viewer. As a consequence of a perspective projection, the dots are faster and ...
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1answer
502 views

In what scenarios and how does GL_ARB_buffer_storage help performance?

The Dolphin emulator for GameCube/Wii has the ability to use the ARB_buffer_storage (or EXT_buffer_storage for GLES) to improve rendering performance. From the extension's description, a GPU driver ...
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0answers
127 views

What quad will fill the screen, which can be inverse-projection-view transformed to map to the near frustum plane?

I've been experimenting with raytracing using GLSL. I had success rendering a cube which encloses the object. Now I want to do a full-screen raytrace, and I want to construct a quad which covers the ...
2
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1answer
320 views

Trading off instancing for render order

I've been doing some searching online and it seems like I could improve my renderer by ordering my draw calls based on depth. For opaque objects render the closest items first and move backward in ...
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1answer
1k views

Why is OpenGL recompiling my depth map vertex shader based on the GL state?

I've written a shader that writes depth to each face of a cube map, as part of rendering cube map shadows for a realtime 3D engine I'm writing with OpenGL and C++. The shader transforms each vertex ...
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1answer
102 views

Weird glColor3f results in framebuffer objects

The code is glColor3f(1, 1, 1); gluSphere(gluq, 0.2, 10, 10); glColor3f(1, 0, 0); glTranslatef(1, 0, 0); gluSphere(gluq, 0.2, 10, 10); In short, when I draw ...
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1answer
331 views

Use glTranslatef and shaders?

In newer OpenGL it's encouraged to use shaders and pass the model-view-projection as parameters. But what if I drew a complex object, and wanted to translate/rotate it and draw many copies? For ...
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1answer
86 views

Represent shape as particles

Input: Triangles which make up an arbitrary shape. Each triangle is represented by 3 3D points. Output: A set of particles which fills up the inside of the object (see image). I have read the ...
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1answer
221 views

Camera position in vertex shader

in the vertex shader I have the vertex position vpos which is in object space and I want to get the vector going from the camera to ...
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2answers
656 views

How can i wrap the earth image around a 3D Sphere using OpenGL, GLFW, GLAD, GLM?

Please help me out with this thing and currently i am a little more than a beginner so please tell me in that context. i don't need any obsolete methods for creating this like using GLUT or GLEW.can ...

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