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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4
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0answers
87 views

Why does accessing a uniform float make my shader more than twice as slow?

My fragment shader was significantly slowed down by a recent change, and I've been trying to understand why. I isolated the main slow-down to accessing a single particular uniform float. If I include ...
3
votes
0answers
108 views

Pyglet: text.Label().draw to FBO?

I just started OpenGL (PyopenGl) & Pyglet 3 weeks ago, and decided to read the Red Book. So sorry if my question shows my lack of comprehension... My question is: Is it possible to display/write ...
3
votes
0answers
437 views

Optimal OpenGL 2D Sprite Batching (Best Practice)

I am working on simple 2D engine using OpenGL (3.3+) for rendering and was wondering what the optimal method of sprite batching would be. I plan to put all sprites into one (or fewer) texture atlases. ...
3
votes
0answers
398 views

Deferred rendering and gaussian blur - artifacts

I compute Gaussian blur in two passes (horizontally and vertically). Shaders look like this: Horizontal blur - fragment shader: #version 420 layout (location = 0) out vec4 outColor; in vec2 ...
3
votes
0answers
472 views

AlphaToCoverage + Alpha Blending = Artifacts

I'm experiencing a strange problem using OpenGL SampleAlphaToCoverage mode. There are rendering artifacts when using alpha-blending on pixels that have been rendered using alpha-to-coverage - and I ...
2
votes
0answers
96 views

Problem with uniforms in OpenGL

I have a strange problem I can't figure out. On the CPU I have class that handles the material properties for a model. material = new Material(); material->Emissive = vec3(0.1, 0.0, 0.0); ...
2
votes
0answers
75 views

Skybox rendering

I am sorry if this is trivial, but I got into OpenGL just very very recently. I am trying to render skybox (with cubemaps) and this is what I have done: Created a VBO with vertices positions (36 ...
2
votes
0answers
47 views

Text rendering overlap

I'm trying to display text with a texture and font description created with BMFont in OpenGL 3.3, but whenever I display the text there is some overlap between certain characters. Here is the text at ...
2
votes
0answers
40 views

problem loading Collada DAE model using Assimp in OepnGL 4.4

I am loading a model in my OpenGL application using Assimp library like this : bool CGameObject::LoadModelFromFile(char* sZFilePath) { std::string fn = sZFilePath; std::string td = "\\"; std::string ...
2
votes
0answers
23 views

Render on texture with alpha 0 for the background colour

Sorry if the question is stupid but I am very new to opengl. I render on a target a scene with a couple of object on a background that is nothing more than the clear colour (which is ...
2
votes
0answers
36 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 ...
2
votes
0answers
227 views

Blank texture in Frame Buffer Object in Deferred Rendering

I'm running the tutorial 35 from olgdev.atspace.co.uk, and it's so strange that the result is a blank screen. This tutorial is performing the first step of Deferred Shading, which means decoupling of ...
2
votes
0answers
817 views

Arcball 3D camera

I have checked multiple threads before posting, but i havent been able to figure this one out. Ok so i have been following this tutorial, but im not using glm, ive been implementing everything up ...
2
votes
0answers
70 views

uniform z slices in clip-space

1) Context I'm using a regular OpenGL perspective projection matrix created with GLM (glm::perspective) and taking the inverse (glm::inverse) to transform clip-space back into view space (and world ...
2
votes
0answers
322 views

glFramebufferTexture2D gives corruption with cube map textures

I am using glFramebufferTexture2D with cube map textures but it gives corruption in texture. draw_cube() function works perfectly when i draw that on default framebuffer. GLenum ...
2
votes
0answers
329 views

Per fragment lighting with OpenGL 4.x tessellated model

I'm experienced with OpenGL 3+. I'm dabbling with tessellation shaders and have now got to a point where I have a nicely tessellated teapot/plane demo (quick look here) As can be seen from the ...
1
vote
0answers
27 views

Variance shadow maps less blurred than normal shadow map

I've implemented VSM (and also ESM) in my engine but results are for me not as I expected and saw in many examples published on network. I set filtering of shadow maps to GL_LINEAR but when I compare ...
1
vote
0answers
36 views

Shadow map shimmering, indexing outside the shadow map

I have tried to reduce shadow shimmering/flickering using technique described here: http://msdn.microsoft.com/en-us/library/windows/desktop/ee416324%28v=vs.85%29.aspx I works as I want and shimmering ...
1
vote
0answers
43 views

Easy way to set face colors with indexed VBOs?

I'm loading OBJs, which lend themselves well to setting up as indexed VBOs, since each vertex is only defined once and then a face definition will reference the same vertex more than once when they ...
1
vote
0answers
62 views

Rotating a scene around a fixed axis

I am looking for a way to move my scene so that when I translate forward/back/left right it moves directly up/down/left/right on the screen. Currently it does do that until I rotate (by anything ...
1
vote
0answers
21 views

Android OpenGLES, getting number of fragments passed depth test/Occlusion Query?

Afeter reading many blogs and searching on Internet, I did not get any sloution for getting number of fragments/pixels which are occludded or not occludded of the object on OpenGL ES3.0 Android ...
1
vote
0answers
85 views

OpenGL - Texture disappears

I'm making a simple program with C++, SDL and GLEW. So far it is going great but I ran into a weird problem. One of my four textures would not show up on screen even though it used the same code as ...
1
vote
0answers
117 views

Is it reasonable to use a 2D texture as a lookup table in GLSL

I need a lookup table in a shader. The input values would be color values and the output other color values. Something like: uniform float lut[256]; color = vec3(lut[int(color.r*255.)], ...
1
vote
0answers
108 views

implementing shadows into my 2D GLSL-based lighting system

I'm writing a lighting system in OPENGL using GLSL shaders, and I'm pretty happy with the light casting I have so far, but I'm totally stuck on casting shadows. Everything I've found online on this ...
1
vote
0answers
56 views

OpenGL seems to be getting its colour from the wrong array on some machines

I have a OpenSceneGraph application which displays a 2D mesh and allows the user to make selections on triangles and vertices and colour them. If you aren't familiar with OpenSceneGraph, it's basiclly ...
1
vote
0answers
78 views

OpenGL/GLM Camera

I want to make a camera that can freely look and walk on X/Z plane and rotate 360 degrees. I'm using OpenGL and the lookAt function from the GLM library to create the view matrix. I've looked through ...
1
vote
0answers
96 views

How to shade hair (line segments) correctly in GLSL

I render my hair geometry in line segments. The problem I have is with the correct shading of the hair. From what I've read I understood that I need the direction of the line segment and the ...
1
vote
0answers
75 views

Creating a voxel chunk with a VBO - How to translate the coordinates of each block and add it to the VBO chunk?

I'm trying to make a voxel engine similar to minecraft as a little learning experience and a way to learn some opengl. I have created a chunk class and I want to put all of the vertices for the whole ...
1
vote
0answers
88 views

Different way to pass uniforms to seperate draws in glMultiDrawElementsIndirect

Given OpenGL version 4.3 and GLSL 430, what would be the best way to pass a matrix to each model in a draw call to glMultiDrawElementsIndirect? I am thinking of going the way of a TBO and indexing it ...
1
vote
0answers
87 views

Android: Hardware Scaler

I was reading through this: using-hardware-scaler-for-performance and am a little confused by it. It says all you need to do to invoke the scaler is to set it like so: surfaceView = new ...
1
vote
0answers
159 views

How can I reduce draw calls when using glBufferSubData and DYNAMIC_DRAW?

At first I had the problem where I had about 150 rectangles rendered every tick. I only used STATIC_DRAW and glBufferData. I added support for DYNAMIC_DRAW and glBufferSubData and now I have a very ...
1
vote
0answers
78 views

Text alignment in OpenGL with FreeType2

I'm trying to implement font rendering and have got into some trouble with glyph metrics. Here's the code where I get the metrics: Glyph gl; gl.width = face->glyph->metrics.width / 64; ...
1
vote
0answers
106 views

What's the best way to set up an OpenGL draw loop in windows?

On mac os x, there's a way to pass the system a function pointer that is triggered at an ideal time to start your drawing code. These are the CVDisplayLink tools. I'd like to understand how to do ...
1
vote
0answers
74 views

Converting signed normalized integer to unsigned normalized integer image format

Given I have my texture data in client memory as signed normalized integers. I want the samples in the shader in the range [0,1]. Can I simply specify: format = GL_RGBA; internalFormat = GL_RGBA8; ...
1
vote
0answers
91 views

3D Camera Y-Axis wrong angle

I am trying to build a camera class, though I am running into a problem. When I move the camera above/below, and try to move towards the ground, I am moved off in what seems to be about 45 degrees in ...
1
vote
0answers
204 views

opengl volumetric billboard implementation: general idea + geometry shader

A while ago I decided to implement the volumetric billboards technique in my university project (C++ & OpenGL 4.3). I passed the subject but failed to implement the mentioned technique. I'd like ...
1
vote
0answers
201 views

Rendering portals using stencil buffer

Due to this question I have changed the method of rendering portals. Before I was using FBO and rendering to a texture, but somehow I failed. Now I switched to a stencil buffer method. My problem is ...
1
vote
0answers
123 views

Shadow maps, reducing “shimmering”

I'm doing shadow maps, and my shadows move around, "shimmer", when I move around the camera. It is difficult to spot on still images but very much noticable in motion. I read an MSDN article ...
1
vote
0answers
145 views

How to fix problem in serpentine case using Blinn/Loop algorithm

I'm trying to implement Blinn/Loop algorithm to render cubic bezier on shader. I calculate the curve type using code below (v0, v1, v2, v3 are cubic bezier segment): CurveType ...
1
vote
0answers
81 views

FreeGLUT keyboard IO timing and synchronization

Using FreeGLut's keyboard callbacks, glutKeyboardFunc(); glutKeyboardUpFunc(); glutSpecialFunc(); glutSpecialUpFunc(); When in the glutMainLoop pipeline do these functions get called? In other ...
1
vote
0answers
52 views

Sampler object not changing texture filter

I am currently binding a sampler object to a texture (GL_TEXTURE12 to be specific) with glBindSampler(12, sampler); and the initial settings are very visible compared to the textures own settings. ...
1
vote
0answers
88 views

Texture not visible on particles

This is the first time I am working with particles (GL_POINTS) I am using kinematic equations and controlling their movement in vertex shader. I am following an example given in OpenGL 4.0 Cookbook ...
1
vote
0answers
203 views

GLSL, Internal error: assembly compile error for fragment shader at offset 513

My vertex and fragment shaders link correctly. When I try and link my shader program I get the error: "Internal error: assembly compile error for fragment shader at offset 513". Pastebin of fragment ...
1
vote
0answers
203 views

Unity Pro - Shadow rendering issue

I am using Unity Pro 4.2.1f4 and I always have this sort of glitch. This is due to the shadows and the bias. Even with a low bias this is happening. I've found a thread that talks about that ...
1
vote
0answers
382 views

c++ opengl unproject not working

first of all, sorry for the bad english. I need to convert my mouse coordinates to world coordinates, I'm trying to use the glm unproject method. 1280x720 is the size of the window, It's hard coded ...
1
vote
0answers
375 views

Geometry shader and triangle adjacency

I'm currently trying to change my project to use GL_TRIANGLE_ADJACENCY instead of GL_TRIANGLES. Following this question, I have managed to construct my index buffer fine, but when it comes to the ...
1
vote
0answers
429 views

How do I mix 3D skeletal animations?

I'm trying to create a 3D-model skeletal animation system for C++/Open GL. I would like to be able to mix animations by allowing animations to only affect specific bones. My game has ride-able ...
1
vote
0answers
90 views

Slick2d font rendering makes all other drawings vanish

I'm converting a java game to lwjgl and slick-utils. I've followed the slick2d examples for font loading/rendering but I found that the font shows as a solid box of color unless I add the following ...
1
vote
0answers
176 views

Rotate a point in 3D space with sine and cosine

I got my camera controlled by the mouse. Now I want a sphere to be always in the center of my view(just for testing). I tried that by assigning the sine of the Y rotation of the camera times 10 as the ...
1
vote
0answers
507 views

Creating a new GLFW window and re-using the old context causes crash

I am using GLFW 3.0.2 and when I want to switch the application to fullscreen, I create a new window and intend to use the OpenGL context of the old window so I don't have to reload all the meshes, ...