OpenGL is a graphics standard and API which targets the desktop and workstation markets. It is designed to be easy to accelerate with dedicated computer hardware, and hence most implementations give greatly improved performance over traditional software rendering. Currently, OpenGL is used for ...

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1answer
21 views

What are the units when reading depth using glReadPixels()?

Suppose I use glReadPixels() to read the depth of a pixel from the depth buffer. What are the units of this? Is it the distance from the camera? Or the distance from the near clip plane? And is the ...
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0answers
22 views

Fixing memory leak in Opengl texture class [on hold]

I recently run my 3D game engine under Valgrin and discovered that everything's almost fine, except that I leak 7,862 bytes in my opengl texture class... I think that I'm not calling a specific opengl ...
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1answer
87 views

Collision between a sphere and a mesh(height-map)

I am trying to implement a method that detects the collision between a sphere and a mesh and reflects the vector of speed. I have a method, that detects a collision between a sphere and a triangle and ...
1
vote
2answers
253 views

Tiled Rendering - Projection matrix

I'm trying to figure out how to perform tiled rendering of my 3d scene (OpenGL). The motivation is to cut the scene up into several textures, combining them into a single image for saving at a very ...
0
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1answer
8 views

Passing data into a vertex shader for perspective divide

In OpenGL and GLSL, I am just learning about perspective projection and the vertex shader. However, I am a little confused about what data actually needs to be passed to the vertex shader, and what ...
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0answers
15 views

Perspective divide: Why use the w component? [duplicate]

In OpenGL, I have read that a vertex should be represented by (x,y,z,w), where w = z. This is to enable perspective divide, whereby (x,y,z) are divided by w in order to determine their screen position ...
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0answers
15 views

GLFW - Event Polling System

I need some help on design. I'm making an event polling system, where a window is notified of events as they happen. I handle events at a system level in my GLFW backend, by using callbacks. ...
3
votes
1answer
154 views

FBX Importer - Vertex Color

I imported vertex positions, indices and normals successfully in OpenGL using fbx sdk, but I just can't figure out how to import vertex colors. I tried to fetch the pointer to array of colors trough ...
28
votes
5answers
15k views

why would you use textures that are not a power of 2?

In the early days of OpenGL and DirectX, it was required that textures were powers of two. This meant that interpolation of float values could be done very quickly using shifting and such. Since ...
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2answers
23 views

Render specific part of a texture in OpenGL (2D Sprite Sheet)

I've looked at this answer to find out how to render just a part of a texture: http://stackoverflow.com/questions/6884285/c-opengl-render-part-of-an-image I tried that, but the problem is, this is how ...
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votes
1answer
27 views

OpenGL Core profile - Array of arrays in glBufferData for VBOs

I want to send each face as VBO, and I structured the data as this facevbo[0] = x x x x x x //x,y,z,r,g,b,s,t facevbo[1] = x x x x x facevbo[2] = x x x x x x x facevbo[3] = x x x x . . . ...
8
votes
1answer
231 views

Tone mapping and eye adaptation - pale colors and darker image

I'm trying to implement tone mapping along with eye adaptation and HDR. Actually I implemented this already but I'm not satisfied with result and I think that I made something wrong. My final image ...
2
votes
1answer
30 views

OpenGL ES God Ray Precision error

I have encountered the following (i think) precision error. (missing link need 10 rep) My source of inspiration was: (missing link need 10 rep) On the PC everything works fine, but on android it ...
0
votes
1answer
189 views

Trying to implement Camera

I'm trying to implement a Camera class in order to walk and look on the world as follow: #ifndef _CAMERA_H_ #define _CAMERA_H_ #include <glm\glm.hpp> class Camera { public: Camera(); ...
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0answers
30 views

Raytracing in OpenGL

I've been looking through some raytracing information recently and I have a question. I think the only way to do raytracing in OpenGL is to use the compute shader, right ? But does it have the luck of ...
0
votes
0answers
29 views

Image speeds up while moving and or rotating instead of constant speed

I'm having a problem with rotating/moving an image. I've set one of my images to rotate on it's z-axis buy updating the angle, but when I run my game, the image starts slowly starts to rotate from a ...
0
votes
0answers
13 views

OpenGL, glDrawElementsInstanced behaving differently on NVIDIA GPU than AMD

I have an AMD GPU on my desktop, AMD HD 5770. I am working on a project on my desktop for over a year. In the scene, I have instanced grass and instanced trees. Everything is working fine on desktop, ...
0
votes
1answer
87 views

Small text is very light / faint with FreeType and OpenGL

I'm able to render large text with FreeType just fine: But when I want to render small text (and the only parameter that changes is the font size), the quality is much poorer: As you can see, ...
1
vote
1answer
32 views

Nvidia Nsight 4.6 VS Edition. The Graphics debugger can't find glew32.dll

I'm trying to debug some textures and FBO's with Nvidia Nsight 4.6 VS Edition. But when I select either "Start CUDA debugging" or "Start graphics debugging" I get an error. "The program can't start ...
0
votes
1answer
80 views

Java OpenGL Perspective matrix not working

I'm trying to render a simple triangle with OpenGL in Java using LWJGL3. Everything is working great, but the projection matrix (perspective) is not working. In C++ I just used to apply the ...
0
votes
1answer
23 views

glGenArrays - This functionality is not available

Whenever I call glGenVertexArrays(), I get the following exception: Exception in thread "main" java.lang.IllegalStateException: This functionality is not available. at ...
0
votes
1answer
102 views

How to Load a Level for use with the Bullet Physics Library

I am trying to use a level in .obj format loaded with Assimp to generate a btBvhTriangleMeshShape to use with the Bullet physics library. I can successfully load btConvexHullShapes as well ...
0
votes
1answer
81 views

How to clip or mask entity in adnroid/andengine?

I want to implement masking with sprite in Andengine. I want same functionality as in ios class called SKCropNode which works like an masking node! Is there any workaround like this in ...
0
votes
0answers
31 views

Open GL 3.3 quad not drawing

Right Now I'm just trying to draw a quad(Latter will draw a texture on it) but for some reason its not showing up. My clear color is working so openGL is working. I don't want to focus on any shaders ...
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0answers
27 views

Modern OpenGL Sprite Drawing - Not Rendering

I'm trying to render sprites based of this tutorial, in LWJGL. Here's what I have so far, with descriptions of what class I use: Transformable2D is a class that holds transform matrices meant for ...
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0answers
13 views

OpenGL 3.3 is not clearing color

When I open the window its show nothing with a white background. I tried earlier to draw a triangle and nothing shoed up. I belive for some reason OpenGL is just not displaying. Maybe I need to ...
0
votes
0answers
19 views

OpenGL, Multithreaded loading/streaming of data

I've thought about how i could implement loading of data in a second thread for two reasons, first, so i can show a nice loading-screen with progressbar and second, for openworld streaming. I came up ...
1
vote
1answer
43 views

Instanced rendering with ARB_vertex_attrib_binding

I'm trying to separate the vertex format specification from the vertex data. I was able to do that for the mesh vertices successfully. For instanced rendering I wanted to further separate the instance ...
0
votes
2answers
1k views

OpenGL : Suggestion on handling collision detection and vertex data?

I was thinking how to do collision detection in my OpenGL application and came to conclusion that I should keep two copies of my geometry data. 1)First copy : Only for OpenGL rendering purposes.This ...
1
vote
1answer
184 views

SDL & OpenGL - Artifacts when multisampling

Im trying to render a model with anialiasing using OpenGL and SDL, but when I do I get strange artifacts. When I render with antialiasing disabled everything looks fine. When antialiasing is ...
2
votes
0answers
47 views

OpenGL picking performance: ray casting vs. color picking

I am curious of how the performance of color picking compares to ray casting. I am looking at the scenario when the mouse is clicked which means only then the scene is rendered in a backbuffer for ...
0
votes
1answer
62 views

What's better - drawing every interval that the window updates, or drawing when necessary and updating when drawing?

So what's better? In case the title is a bit confusing I mean: 1) Drawing every window update interval. For example, for a 60FPS window, every 17 milliseconds. For example: ...
0
votes
2answers
78 views

Fragment shader compiling in webGL but not in OpenGL

I am programming in Haxe (language compiling to multiple platforms) and I have written some shaders. My fragment shader runs fine in html5, but when I try to compile for native (OS X and/or Neko, a ...
3
votes
1answer
331 views

Using textureGrad for anisotropic integration approximation

I'm trying to develop a real time rendering method using real time acquired envmap (cubemap) for lightning. This implies that my envmap can change as often as every frame and I therefore cannot use ...
1
vote
2answers
73 views

Smallest, most memory-efficient way to have tiles? (C++/OpenGL)

I need to have tiles in my game, just 16x16 images, there would be hundreds (or even thousands) that make up a level. Of course it's not viable to have thousands of memory-hog normal entities, but ...
0
votes
1answer
35 views

Best approach for level specific textures

TL;DR: Best way to handle level-specific textures without overkilling memory usage and killing performance and keeping things clean in OpenGL for mobile (also lower-end devices) and desktop using ...
0
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0answers
41 views

Object Rotation with mouse around his axis using Quaternions

I faced a couple of days ago a gimball lock problem , trying to rotate an object on openGL 2.1. I have done some researches and found out that Quaternions could help me. So I implemented the class ...
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votes
2answers
66 views

Cant decide on openGL 2 or 3 for 2D game engine [closed]

Hi I want to make a 2D game engine. I want to make this engine to learn lower level code. I cant decide If I want to use OpenGL 3.x or 2. The engine should support Linux, MacOSX, Linux, Android and ...
0
votes
1answer
41 views

How to use traditional pixel coordinates system in OpenGL? (with C++/SDL2)

I find the normalized, centralized coordinate system used in OpenGL weird and annoying, is there anything I can do at all to make it work like normal pixel coordinates on everything ever except ...
1
vote
4answers
52 views

OpenGL calls from a different thread?

I understand OpenGL is not thread-safe, but at the same time, Google seems to be giving me mixed responses. I have a LibGDX game that functions normally, UI/rendering/logic on the same thread, ...
1
vote
1answer
39 views

Android OpenGL EGL context lost

I'm developing simple Android game in OpenGL ES 2.0 and the development stage is getting closer to publishing game on play store, but I'm still unsure about EGL context behaviour on different devices. ...
0
votes
1answer
82 views

How should I render multiple objects in OpenGL?

I am just getting my head wrapped around modern OpenGL. Let's say that I would like to draw 10 objects, how would I structure that? Would I call glDrawElements(...) in a for loop 10 times? void ...
0
votes
2answers
61 views

How do I start and stop a GLSL shader?

Is there a way to start and stop a shader?. I want to use this shader to sweep once over my texture and then stop. Does anybody know how to do that? void mainImage( out vec4 fragColor, in vec2 ...
0
votes
2answers
118 views

GL_SPOT_CUTOFF not working properly

I'm new to OpenGL. I'm studying OpenGL 2.1 and I'm trying to make a little program to test the GL_SPOT_CUTOFF property, but when I set a value between 0.0-90.0, the light doesn't work and everything ...
1
vote
1answer
30 views

OpenGL 4.5 Primitive Restart vs. Base Index

From how I understand the two techniques (Primitive Restart and Base Index) explained on https://www.opengl.org/wiki/Vertex_Rendering , they both do the very same thing. Simply spoken, they allow me ...
0
votes
1answer
178 views

DirectX11 Equivalent of OpenGL code

I am currently porting parts of my engine over to D3D11 from OpenGL and was trying to figure out how I would accomplish the following blending functions in D3D11. glEnable(GL_BLEND); ...
56
votes
7answers
22k views

Good resources for learning modern OpenGL (3.0 or later)? [closed]

I stumble upon the search of a good resource to start with OpenGL (3.0 or later) . Well, I found a lot of books but none of them can be considered a good resource! Here two examples: OpenGL ...
2
votes
0answers
81 views

OpenGL 2.1 rotation , Gimball lock

I'm working on a little app for a school project , which should be manipulating 3D objects. And i'm stuck with the rotation , as i'm facing what i think is called the gimball lock ? here's a video I ...
0
votes
1answer
24 views

Open GL: How to map point inside frustrum to normal device coordinates (NDC)?

I read this article http://www.songho.ca/opengl/gl_projectionmatrix.html. It's explain how calculate projection matrix coefficients. But I completely can't understand how author perform mapping from ...
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0answers
27 views

Help with Zoom in Functionality in Mandelbrot set

I was able to create Mandelbrot set. Now, I want to zoom in and out and can use left right key to navigate. Here is my code. #include <windows.h> #include <iostream> #include ...