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
211 views

How do I add a border to rectangles using a shader?

I want to draw some rectangles with a border. Currently I render the fill with glDrawArrays(Triangles, ...) and the border with glDrawArrays(LineLoop, ...). Is there a neater way? I'm targeting ...
1
vote
1answer
118 views

Correct multiplication order for a 2D Matrix

I'm currently trying to create a camera and entity/model matrix for my 2D game similar to that of Unity3D. I've already tried to find answers to this question on stackoverflow/gamedev but i couldn't ...
3
votes
2answers
135 views

Rendering Many Objects in OpenGL4

Sorry for asking such a basic question. I am reading books on OpenGL4 but in most examples they generally render only objects. So I understand how to deal with vertex buffers and vertex array buffers, ...
6
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1answer
207 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 ...
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1answer
139 views

3D position of an arbitrary UV coordinate

I have a UV map for a 3D mesh that encodes "links" between pairs of UV coordinates. I have previously defined this links (or pairs), one to one. The links are enconded using the function rgb_color(u1, ...
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1answer
34 views

Swapping Framebuffers or swapping attachments?

I wanted to know what the better approach would be for post-processing: swapping between framebuffers or swapping between textures attached to one framebuffer?
2
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2answers
76 views

How to smooth mask texture edges correctly regardless it's size

I have a texture intended as a mask. The texture type is GL_R32F (32 bit float) and the data inside is a signed distance field (= value of each texel is distance to nearest mask edge). For test ...
2
votes
1answer
153 views

OpenGL ES draw pre-rendered background onto depth buffer

I want to create a scene with 2D pre-rendered background and 3D models for characters (like those classic Final fantasy games). For the background, I have 2 textures: one to be displayed, with ...
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0answers
33 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 ...
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1answer
70 views

Applying transformations in Geometry Shader

So, I am trying to program in opengl (3.3) a kind of robot. The idea is that I have some simple blocks that represent his body (4 rectangles for his arms, one for the torso and the last one ...
3
votes
1answer
339 views

OpenGL - Drawing multiple meshes at once using VBOs and IBOs

I have been learning OpenGL 2.1 but using shaders, VBOs, IBOs, etc. I have gotten a rendering engine that can load and draw meshes, materials, forward lighting (no shadows yet), SceneNodes, and ...
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0answers
108 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 ...
2
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1answer
81 views

Selection with region (when rendering with shaders and VAO)

I am currently render my geometry using "Modern OpenGL" approach (with shaders and buffers). I have already implemented picking of single primitives using glReadPixels. Now I am faced with problem how ...
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1answer
148 views

Draw selected instances of VAO (glDrawArraysInstanced)

I'm using glDrawArraysInstanced to draw multiple instances of a tree at different positions to generate a forest. Is there a way to draw selected instances? For example: I got 100 trees with ...
3
votes
1answer
210 views

glm direction vector rotation

I'm working on a flight simulator, but I'm stuck with my airplane orientation. I tried some things but noone worked correctly. This is what I have : To be able to move it and roll it around himself, ...
2
votes
1answer
59 views

How to know when graphics driver or card changes

I'm about to start work on implementing GLSL binary shader compilation and I was curious how to handle the cases when the shaders need to be recompiled, such as when the driver (or perhaps even the ...
0
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1answer
93 views

Blurring part of the screen - optimisation

I develop 3d menu and sometimes I need to blur only part of the screen. I use a forward rendering. I create a frame buffer object with 3 color attachments. Rendering looks like this: bind fbo ...
1
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1answer
33 views

Only affect pixels in buffer with alpha 0

I'm working on a transition effect where I have a texture and simply draw that as a pattern to my buffer. Here is a demo, use "e" to start the effect again. This looks fine but it won't work if the ...
0
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2answers
115 views

What does glMultiDraw* do?

I'm having trouble understanding exactly what glMultiDraw* does, and when it should be used. Is it to be used if I have one VBO with multiple objects in it or do I use it with many VBO's? It would ...
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0answers
97 views

Fixing/avoiding Z-fighting with decals OpenGL

I'm trying to draw animated flames as a decal in OpenGL (just a simple quad with an animated texture as a decal on another quad). Problem is as the camera moves away I get terrible Z-fighting in the ...
1
vote
1answer
128 views

OpenGL Compute Shader Uniforms

I am trying to use a compute shader to generate some data in a texture. My compute shader looks something like this: #version 430 //uniform int u_CurrentMipSize; const int u_CurrentMipSize = ...
2
votes
0answers
81 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 ...
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votes
2answers
1k views

How many OpenGL programs should I use to render multiple objects?

My scene has multiple objects in it. (Let's say 3 cubes, 1 cylinder, 8 spheres.) I assume I should create a vertex shader for each. How many programs should I have? Alternatives: One program per ...
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0answers
170 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.)], ...
5
votes
1answer
203 views

“Normal” Blend Mode with OpenGL Trouble

I've been having a lot of trouble trying to get a OpenGL blend function to work as I'd expect it to with like what I'd expect (or from any sensible image editing program). As an example, I'll use ...
1
vote
1answer
99 views

Lookup table in shader opengl es

What I need is apparently very simple, a lookup table in a fragment shader. It seems that the natural way would be an array float lut[], but in some implementations of OpenGL ES I am getting an error ...
2
votes
0answers
26 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 ...
7
votes
2answers
213 views

How to avoid subpixel values in a resolution independent 2D game with orthographic projection?

I'm trying to do resolution independent rendering of moving sprites in a 2D game. My plan is work in a fixed coordinate system in my world (for example 960x540) and use orthographic projection to ...
1
vote
1answer
53 views

Using depth texture for depth testing

I was wondering if it is possible to render my scene onto a depth texture then using that texture for depth testing in another pass. I have an idea to that in shaders, but is that possible ...
0
votes
0answers
71 views

Gaussian blur not working correctly

So pretty much I tried to add a gaussian blur to something I am making and it is acting oddly. The setup is like: [All framebuffers are cleared to rgba(0,0,0,0), normal blend enabled] Draw some solid ...
1
vote
1answer
128 views

Vertex shader in OpenGL/GLSL - transformation of the interior of a textured quad

I have a LWJGL project and ran into a problem with a vertex shader I wrote. In my scene I am rendering a map whose ground consists of rectangular tiles. On top of that there are other objects (I used ...
2
votes
1answer
204 views

Anti-Aliasing in OpenGL [C++]

I'm trying to make anti-aliasing work inside of OpenGL, here's what I've tried: glEnable(GL_POINT_SMOOTH); glHint(GL_POINT_SMOOTH_HINT, GL_NICEST); glEnable(GL_LINE_SMOOTH); ...
0
votes
1answer
72 views

Proper way to encapsulate a Shader into different modules

I am planning to build a Shader system which can be accessed through different components/modules in C++. Each component has its own functionality like transform-relevated stuff (handle the MVP ...
0
votes
0answers
53 views

OpenGL textures trigger error 1281 if SFML is not called

I am using SOIL to apply textures to VBOs, without textures i could change the background and display black (default color) vbos easily, but now with textures, openGL is giving an error 1281, the ...
1
vote
1answer
76 views

Problems with texture orientation in space

I am currently drawing texture in 3D space and have some problems with it's orientation. I'd like me textures always to be oriented with front face to user. My desirable result looks like ...
0
votes
2answers
65 views

Best way to detect if vec3 is between vec3(x) and vec3(y) in glsl

As titled I am sampling from a texture and if the color is somehow gray [vec3(.8), vec3(.9)] and an uniform is 1 I need to substitute that color with another one I am not a glsl veteran but I am ...
0
votes
1answer
110 views

Orthographic Projection Issue

I have a problem with my Ortho Matrix. The engine uses the perspective projection fine but for some reason the Ortho matrix is messed up. (See screenshots below). Can anyone understand what is ...
5
votes
1answer
566 views

glDrawElements vs glDrawArrays for polygons that do not reuse vertices

Is it better to use glDrawElements or glDrawArrays when not reusing vertices? There must be some difference, otherwise people would always use glDrawElements? I suppose the question could be ...
0
votes
1answer
86 views

Doing a turntable camera animation on a world matrix rather than view matrix

I have a camera class that contains a 4x4 view matrix as a member variable. Most of my camera controls work fine when doing them directly on the view matrix. In an attempt to unify all of my scene ...
1
vote
2answers
256 views

How to detect graphics API at runtime with SDL2?

Using SDL2, is there a way to determine at runtime whether the application is using OpenGL, OpenGLES, or DirectX? EDIT: If there is a way to figure it out without using the SDL2 API, I'm willing to ...
0
votes
2answers
180 views

How many normals are needed to have a smooth surface?

I'm trying to draw a smooth cloth surface and I have a per-pixel shader. I expect to have a smooth surface but it's not the case. I think the problem comes from my normals. The image show the surface ...
0
votes
1answer
189 views

How can I prevent the viewport from stretching/distorting?

Basically, I want to know how I can remove distortion or stretching of the rendered image when the viewport/window size changes. The following images exemplify the distortion/stretching I'm talking ...
0
votes
0answers
39 views

GLSL 150 (or upper) per pixel lighting base code

I'm looking for a working example of smooth per pixel shading for one directional light I've seen this example http://www.opengl.org/sdk/docs/tutorials/ClockworkCoders/lighting.php but its old GLSL ...
1
vote
1answer
153 views

Game development for high-school with C++ and OpenGL [closed]

I've been teaching high-school students (12th grade) game programming in the last 2 years. The way I did this till now, was first to give them "half made" classes (for Point, Polygon, etc.) and ...
1
vote
1answer
86 views

Does scaling affect performance in OpenGL? [closed]

I've never been able to understand the best practice in this context. I usually want to ship my game with as minimum size as possible. So whereever possible, I try to use scaling of my graphics. Let's ...
0
votes
1answer
108 views

NiftyGUI - Text isn't rendering

I am trying to create a gui with nifty on top of lwjgl. I've already had some problems during the Nifty setup, however now Nifty is set up and running correctly but for text rendering. Here is my xml ...
5
votes
1answer
320 views

How can glass breaking effect from Smash Hit be achieved? [duplicate]

I saw Smash Hit the other day and was amazed by the physics of the game, specially the shattered glass effect: I've read other posts about this subject but I still feel that they don't share enough ...
2
votes
1answer
44 views

Rendering a mesh in image viewport

I have a mesh made of nearly half to a one million vertices. I also have some 6-DoF camera poses around this mesh. At these poses I'd like to find out which of the 3D points of this mesh get projected ...
4
votes
1answer
168 views

How to calculate directional light frustum from camera frustum

I'm playing around with OpenGL for a few weeks now. For the following screenshot I picked the glm::ortho values for my lightsource by trial and error. There are two directional light sources with ...
2
votes
2answers
194 views

Water silhouette shader using GLSL

I have this problem to solve using Cocos2d-x 3.x: In my game there is water represented by rectangle texture, modified by the code on the go. I also have a character moving around, rotating etc. I ...