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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2answers
696 views

How can I create a VBO when I don't yet know how many vertices it will contain?

I'm trying to convert my 3D block work rendering from immediate mode and display lists to VBOs. I'm having trouble understanding how to properly handle creating the buffers: I really don't know how ...
2
votes
0answers
446 views

Help with 2D sprite instancing [closed]

Alright, so I'm pretty new to OpenGL programming. I've been writing my own engine, initially using the fixed function pipeline. I then did a 1:1 replacement of the fixed-function methods with shaders ...
2
votes
3answers
195 views

Can I store D3D9 textures so that they don't consume process memory and also don't require “lost device” handling?

I have an OpenGL application that uses a lot of texture memory. While the texture is stored in the system memory, that texture memory is not part of my application process memory. When this ...
1
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1answer
180 views

Separate shader programs or branch in shader? [duplicate]

I have a bunch of point lights and directional lights. Instead of checking the light type in the fragment shader and then branch for either point light calculation or directional light calculation, is ...
0
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2answers
342 views

How forward rendering done using OpenGL?

Recently I come across the term forward rendering. I'm kind of curious how this could be done in OpenGL. I have done a lot of search on this, majority of the result I get are on theory but not code ...
3
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1answer
383 views

Solving banding with additive blended particles

I needed to implement particles for my 2D game, written in C++ with OpenGL for graphics, so I went ahead and created a nice geometry container to batch particles together and then implemented the ...
0
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1answer
127 views

How can I improve the rendering speed of procedurally-generated curved shapes (while keeping them smooth)?

I'm trying to render a large, procedural-generated shape with OpenGL, but I'm having some issues. I'm rendering the shape by composing it from many cubes, as follows: int TRACK_MIDDLE2 = 107; for ...
0
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1answer
173 views

Material properties and deferred renderering

I'm using assimp to import 3d models, and each model defines a set of material properties as well, such as material diffuseColor, ambientColor, specularColor and emissiveColor. Where would I store ...
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2answers
508 views

Tangent on generated sphere

I have difficulties understanding the tangent/bitangent concept for normal mapping, or rather the calculations of them. I draw a sphere which is generated with the code in the OpenGL redbook ...
1
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1answer
827 views

glGenerateMipmap confusion

I'm trying to get a grip on mipmaps with OpenGL. I believe I understand the concept, but when trying to have OpenGL generate them I wonder how it determines how many mipmaps to generate? Here's what ...
2
votes
1answer
338 views

How can I improve the performance of texture switching without resorting to atlasing?

I'd like to use texture images that are not a sprite sheet or other form of texture atlas, mainly because I'll be consistently adding and swapping textures while I figure out the direction my game ...
3
votes
1answer
398 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 ...
0
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1answer
504 views

glRotatef rotation never applied to 3d cube

I have a floating cube that I want to rotate around the Y axis. The cube renders fine, the proper size, the proper coordinate, the proper texture/faces, etc. However, the rotation is never applied. ...
0
votes
1answer
34 views

Versions of GL and its device that don't display or required powers of 2 for the sprites

From this question aside from identifying possibilities of displaying images that don't needed to require powers of 2, what are the versions of GL that can actually display images even if don't needed ...
0
votes
1answer
114 views

Is it possible to display no white images/sprites when using the latest Android OS?

Was it okay to use Texture.setEnforcePotImages(false) in order to disable conditional width and height pixel size that requires power of 2? I'm planning to sell the game app at Google Play. I want to ...
0
votes
3answers
419 views

Encode two integers into colour values and compare them in a HLSL shader

I am writing a 2D point and click adventure game in Monogame, and I'd like to be able to create an image mask for every room which defines which parts of the background a character can walk behind, ...
6
votes
2answers
2k views

How do OpenGL's texelFetch and texture differ?

I understand the main differences between texelFetch and texture, but have some questions about the details: Does texelFetch involve a performance penalty? Such as not using a cache or such? Are ...
1
vote
1answer
853 views

View to normal calculation in GLSL

Sorry for the terrible title, but I really cant think of anything better.. Suggestions welcome. I am trying to do something like showcased in this video: http://www.youtube.com/watch?v=CaTI2d0tQME ...
0
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1answer
194 views

Why am I seeing undesirable rendering results using VBOs like this?

I am trying to write a program that renders using VBO(vertex buffer objects). Everything works great except that when I run the program, It looks like the object is spazzing out. I think its due to ...
1
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1answer
2k views

Basic Car Movement, Converting 2D Vectors to 3D problems

I'm trying to follow this guys method for steering a basic car. Link. It's the first example I can sort of get my head around and I'm trying to convert it to a working 3D version. To get some scope, ...
0
votes
1answer
93 views

Blending and shadowmapping?

I am trying to implement shadow mapping, and currently I have 2 point lights and 1 global ambient light source and my rendering loop looks roughly like this (the details are not relevant): void ...
6
votes
2answers
944 views

Atmospheric scattering and sky geometry

I'm trying to implement an atmospheric scattering in my graphics (game) engine based on the GPU Gems article: link. An example implementation from that article uses a skydome. My scene is different - ...
0
votes
1answer
113 views

Storing attributes in static geometry

I have a Minecraft like world where I statically create one instance of each tile type, and then place it around the world. However, I don't know how to actually change individual attributes for each ...
1
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1answer
487 views

How can I handle errors when there is no valid OpenGL context?

I'm writing cross-platform (iOS, Android, OSX, Windows) library code that draws its output using OpenGL. I expect my users will often try to call my library's rendering functions without a valid ...
2
votes
1answer
593 views

glDrawArrays (layered rendering using geometry shader) only draws one point

I have been debugging this for a while but I can't seem to find the issue. I created a framebuffer for layered rendering like this GLuint buffer; glGenFramebuffers(1,&buffer); ...
1
vote
1answer
46 views

Drawing behavior when a fragment is written to multiple times in a single pass

This seems really basic, but I'm confused and can't find a clear answer anywhere. What happens to a target fragment of a rendertarget if the fragment is written to multiple times within one pass ...
14
votes
2answers
2k views

What are the common rendering optimization techniques for the geometry pass in a deferred shading renderer? [closed]

I have been developing a game engine using OpenGL 3 and C++ (and glfw for window management). I have advanced so far, got most of the things done except sound entities and optimizations. The engine ...
1
vote
2answers
270 views

Why swapping buffers takes different amounts of time?

When my program starts, almost nothing is on screen, just couple of lights and spheres. My FPS is at ~50. The Speed measurements looks like this: UpdateFrame took 0 ms Clearing lights queue: 0 ms ...
1
vote
2answers
192 views

Application of classes with critical non-static fields in LWJGL [closed]

I'm going to be as specific about this question as I can. Ultimately, how is it that I apply a class that uses non-static fields in LWJGL? More specifically, I know that OpenGL is quite nearly more a ...
-4
votes
2answers
137 views

Is OpenGL just for graphics when it come to game design? [closed]

I am a computer science major interested in learning how to create games. I know c++ very well and I am familiar with opengl. I want to know if opengl is just for graphics or can it be used for things ...
1
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1answer
154 views

SFML image extension for best performance

I am using SFML library in my 2D game. The Texture Class has a method to load an image from file: Texture.loadFromFile("image.*") Which file extension should I use to achieve best performance? ...
0
votes
1answer
203 views

Where to store OpenGL object id:s

When working with OpenGL, you often recieve integer id:s to keep track of OpenGL objects. For example, representing a simple mesh, you may have a number of references to objects like so: GLuint ...
1
vote
3answers
634 views

Optimal number of work groups for compute shaders

In OpenGL, is there a way to dynamically determine the preferred workgroup size of the underlying hardware? Or at least, to approximate it using some queried metrics? In OpenCL, you can do this using ...
1
vote
3answers
201 views

Is it possible to gain performance by omitting vertex normals in the GPU pipe?

I am working on a rendering problem where I want to render as many raw triangles to the screen as I can with either OpenGL or DirectX with the absolute fastest performance possible. I wondered about ...
3
votes
2answers
810 views

When is the Z coordinate normalized in GLSL?

I thought that whenever you transform an object to world space, then view space and finally screen space, the last matrix you apply(the projection matrix) normalizes the z values between 0 and 1. ...
1
vote
1answer
390 views

How does HLSL handle clip(vector)?

My goal is to convert clip() to GLSL, version 1.5. I'm currently doing a basic: if (x < 0) discard; But if x is not a scalar, obviously I can't use the "<" operator. So I'm wanting to ...
0
votes
1answer
207 views

Why do the ALPHA channel in TGA is not visible?

Good morning GDSE, I am loading a TGA using loadTGA function found in superbible 4th edition source code. Here is how the image looks in Gimp You can see I have enabled alpha channel in Gimp, I ...
5
votes
1answer
2k views

Exponential Variance Shadow Mapping - implementation

I use a variance shadow mapping with a "standard" light bleeding fix in my graphics engine which is based on deferred rendering.. I have a single shadow map for a directional light beacause a test ...
5
votes
1answer
453 views

Animation of moving circle by square's outer surface

I want to make this animation in OpenGL, here I attached a simple gif how I want it to looks like: Main problem is that I can not figure out how to move by corner - circle should smoothly move by ...
0
votes
3answers
172 views

directional lightning

I have managed to get a point light working, but I am facing problem with directional lightning. Fragment shader uniform vec4 lightColour ; uniform vec3 lightPos ; uniform float lightRadius ; ...
1
vote
1answer
854 views

OpenGL Texture loaded but wont draw on Bind

I wrote my entire Texture loader by hand. I'm not using any Libraries. From what I gather the loading part is done correctly and stored in the texture class: Texture* TGATextureLoader::create(const ...
1
vote
1answer
179 views

Random lines away from images in java2d opengl game

Working on a java game that uses some pngs images for icons/textures. A few images ( fewer than 5, out of dozens ) are showing some odd parallel "artifact" lines. They move with the image, are ...
2
votes
1answer
1k views

How to select a vertex by mouse clicking in OpenGL?

I'm programming a simple graph game and so far I'm still doing a few tests in OpenGL. Right now, let's say I defined a GL_POINT with the glVertex2f(20.0f, 0.0f). I have this function to calculate the ...
3
votes
2answers
1k views

Identity matrix. Confusion. What does it really do

I understand identity matrix is like multiplying to 1. But i can't really understand why would you multiply an a matrix that will only result to the same. Also im messing up with an OpenGL code and ...
0
votes
1answer
2k views

How to load and draw this *.obj correctly?

I have a loader class for *.obj files (called GLModel) which has 2 main methods - public GLModel(BufferedReader ref, boolean centerit, GL gl,Texture texture) which use for *.obj load , and ...
1
vote
2answers
339 views

Calculating shadowmap coordinates for cubemap in shading pass?

I'm trying to implement shadow mapping with cube maps. I believe I've done the first stage by filling the cube map, but for the final shading pass I am unsure how to exactly calculate the cubemap ...
0
votes
1answer
104 views

How can I animate a portion of the textures on a model?

I have a model to which I have attached multiple textures. Both textures are currently static, but if I want to move (or slide) the texture which is on the top (in UV space), is that possible? Maybe ...
2
votes
1answer
373 views

How does the fragment shader get data from the vertex shader?

How can any interactions between these two shaders work? I mean the vertex shader sends a vertex's color to the fragment shader, but that's only one fragment, what about all the other ones between the ...
1
vote
1answer
609 views

What is the difference between shader uniforms and attributes in OpenGL?

I don't fully understand the differences between uniforms and attributes. To be honest, I probably haven't even used attributes. Can uniforms change for each vertex? I mean to calculate the vertex's ...
2
votes
1answer
256 views

Are ambient, diffuse and specular light or material properties?

Are ambient, diffuse and specular properties of light or material? I am doing ray casting in OpenGL, I've managed to create lit sphere using formula I = L Ka + L Kd (n . l) + L Ks (r . v)^n but I ...