Questions tagged [fragment-shader]

A program that runs on the GPU to determine output colors for pixels. Also known as a fragment shader.

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23 votes
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Why is H (blinn) used instead of R (phong) in specular shading?

I can't find a good reason for this anywhere. The reflection vector used in phong has a simple basis in physics. But the half vector used in blinn seemingly has no rational basis, and does not ...
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23 votes
2 answers
13k views

Do I lose/gain performance for discarding pixels even if I don't use depth testing?

When I first searched for discard instruction, I've found experts saying using discard will result in performance drain. They said discarding pixels will break GPU's ability to use zBuffer properly ...
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19 votes
2 answers
53k views

GLSL - one-pass gaussian blur

It is possible to implement fragment shader to do one-pass gaussian blur? I have found lot of implementation of two-pass blur (gaussian and box blur): http://callumhay.blogspot.com/2010/09/gaussian-...
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19 votes
2 answers
39k views

GLSL Shader - Change Hue/Saturation/Brightness

I'm trying to change the hue of an image using a GLSL fragment shader. I want to achieve something similar to Photoshop's Hue/Saturation Adjustment layer. In the following image you can see what I've ...
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17 votes
2 answers
6k views

How do I write a shader that lights up when objects are near a surface?

In this Overwatch gameplay video, the character's shield lights up white in areas that are near other objects' geometry. Note the white edges on the blue shield, near the floor, walls and pillar. I ...
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15 votes
2 answers
4k views

Toon/cel shading with variable line width?

I see a few broad approaches out there to doing cel shading: Duplication & enlargement of model with flipped normals (not an option for me) Sobel filter / fragment shader approaches to edge ...
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14 votes
5 answers
9k views

What rendering techniques would I use to draw a drop shadow effect for cards in a card game?

What type of shading algorithm might be used to create shadows like these? the one I'm making is similar but it is all done with a 2D drawing API powered by OpenGL so there is no Z coordinate. In ...
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10 votes
1 answer
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How to create a "retro" pixel shader for transformed 2D sprites that maintains pixel fidelity?

The image below shows two sprites rendered with point sampling on top of a background: The left skull has no rotation/scaling applied to it, so every pixel matches perfectly with the background. The ...
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10 votes
1 answer
812 views

How do I implement 2D shadows cast between layers?

How could I implement 2d shadows that are cast by objects in a different layer? NOT like the dynamic lighting in the well known tutorial from Catalin Zima : But like the shadows of the pipes in this ...
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  • 1,259
9 votes
3 answers
2k views

Outline sprites

I'm currently working on a 2D game, and my current task is to outline selected object. I basically use a blur shader to do it fully runtime. I first draw my sprite using a vertical gaussian blur ...
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  • 91
9 votes
1 answer
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Optimizing performance of a heavy fragment shader

I need help optimizing the following set of shaders: Vertex: ...
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8 votes
1 answer
8k views

How do I use screen-space derivatives to antialias a parametric shape in a pixel shader?

In Valve's Alpha Tested Magnification paper, it mentions using "per-pixel screen-space derivatives" for doing anti-aliasing. My understanding is that this is the ddx...
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8 votes
1 answer
2k views

GL ES: Fragment shader optimization

Summary: I get FPS slowdown as soon as I try to tint the sprites (i.e: multiply texture with color in the fragment shader) Details: Hardware: iPod touch 4 I am drawing 700 sprites on the screen ...
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7 votes
2 answers
12k views

How to implement color changing fragment shader?

I have a background of a given size and filled with a given color. I want to change it with an animation effect, starting from the center and spread out until it extends the whole background. The new ...
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7 votes
1 answer
5k views

2D Line drawing with Pixel Shaders

Recently I asked a question, what is the fastest way to render 2D lines using DirectX, and one of the answers mentioned this paper on Fast Prefiltered Lines which uses Pixel Shaders to accomplish ...
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6 votes
1 answer
16k views

In HLSL pixel shader , why is SV_POSITION different to other semantics?

In my HLSL pixel shader, SV_POSITION seems to have different values to any other semantic I use. I don't understand why this is. Can you please explain it? For example, I am using a triangle with the ...
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6 votes
1 answer
8k views

How to make a 2D neon-like trail effect in Unity

Recently I've been toying around with neon-ish effects for a game I'm making and wanted to share my results with you. If you guys have any other methods of achieving this result, please be sure to ...
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6 votes
1 answer
437 views

How do texture lookups for trig functions work?

I have a pixel shader that calculates a mandelbrot fractal. It uses the standard formula: z = z2 + c I'd like to extend it so the power z is raised by varies. To do this i have the following ...
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6 votes
1 answer
605 views

Animating compression wave shader which uses image for displacement map

I've been testing a variety of shockwave or ripple effect shaders, and spent time on this cleaned up and improved version on shadertoy. I'm not entirely satisfied with that because it produces an ...
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  • 909
6 votes
1 answer
622 views

Why does writing to a D3DFMT_R32F render target clamp to 1?

I'm currently implementing a picking system. I render some objects in a frame buffer, which has a render target, which has the D3DFMT_R32F format. For each mesh, ...
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  • 161
5 votes
4 answers
6k views

How many times fragment shader is executed?

I have an OpenGL code, with 3 different shader programs. I have a simple question, I know fragment shaders are executed for every every fragment in the scene. But is there a way using which we can ...
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  • 313
5 votes
3 answers
9k views

OpenGL additive blending not working as expected

I am trying to achieve additive blending with point sprites. When the sprites overlap, all I get is solid red, when I expect to get a smooth blend from red->yellow->white. My sprite texture has all ...
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  • 805
5 votes
2 answers
1k views

Best way of writing pixel manipuliting-intensive applications with OpenGL/Direct3D

Recently I have been making little experiments with engines similar to old Wolfenstein 3D, Doom and Build, engines where the 3D rendering is entirely done in software and therefore you need full ...
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5 votes
1 answer
4k views

using heightmap to simulate 3d in an isometric 2d game

I saw a video of an 2.5d engine that used heightmaps to do zbuffering. Is this hard to do? I have more or less no idea of Opengl(lwjgl) and that stuff. I could imagine, that you compare each pixel ...
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  • 746
5 votes
1 answer
2k views

Better solution for boolean mixing?

Sorry if this question has been asked in the past, but searching Google and here didn't yield relevant results, so here goes. I'm working on a fragment shader that implements both conditional/boolean ...
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5 votes
1 answer
3k views

Stencil buffer VS conditional discard in fragment shader

I have a continuous height-mapped mesh to represent landscape. I also have 1 to let's say 10 wells on this landscape represented by additional models. What I want to achieve is to create an illusion ...
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5 votes
1 answer
815 views

Ashikhmin-Shirley model implementation: ugly result

I am trying to implement the Ashikhmin-Shirley model using these formulas: This is the GLSL 1.2 fragment shader code: ...
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5 votes
1 answer
3k views

How do I achieve supersampling / anti-aliasing in pixel shaders?

I am trying to write a couple pixel shaders to apply to images similar to Photoshop effects. For example this effect: But I noticed there is aliasing in my resulting image (the above image is a ...
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5 votes
1 answer
2k views

Creating Blender-like cavity shader

I'm trying to achieve in Godot something similar to cavity effect from Blender (this can be enabled in viewport options; cube on the left is displayed by viewport with this option enabled): How would ...
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5 votes
2 answers
530 views

Weird shader behavior on different devices

I'm trying to combine an ordinary shader with a Single Distance Field shader (for fonts and scalable icons) into one shader program. The idea is simple - if uv.x is less than 1.0, it is drawn as ...
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5 votes
0 answers
185 views

Raymarching tangents

I've recently started to experiment with raymarching over on shadertoy.com. It seems common to find the normal for a distance field like so: ...
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4 votes
3 answers
979 views

How to read BC4 texture in GLSL?

I'm supposed to receive a texture in BC4 format. In OpenGL, i guess this format is called GL_COMPRESSED_RED_RGTC1. The texture is not really a "texture", more like a data to handle at fragment shader....
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  • 335
4 votes
1 answer
15k views

How do I calculate UV space from world space in the fragment shader?

In my vertex shader I have calculated the world space o.worldSpacePosition = mul(unity_ObjectToWorld, vertIn.vertex); How do I convert that world space into uv ...
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4 votes
2 answers
13k views

Computing pixel's screen position in a vertex shader: right or wrong?

I am building a deferred rendering engine and I have a question. The article I took the sample code from suggested computing screen position of the pixel as follows: ...
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  • 1,551
4 votes
1 answer
776 views

Procedural Hatching

I know that it is possible to make a shader that uses procedural hatching instead of pre-designed tonal art maps. But is it possible to make that procedural hatching in the fragment shader? I would ...
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4 votes
1 answer
128 views

Phantom objects in ray tracing

I am attempting to add volumetric shadowing to an application I am working on to test some things. For this effect I wrote the following fragment ...
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  • 239
4 votes
2 answers
5k views

Algorithm for a rain effect (Shaders)

I'm trying to implement a rain effect using shader, I use godot 3-alpha, which uses a simplified GLSL 3.0 language. But I'm just finding very complex examples for me, I understand little about shaders,...
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4 votes
2 answers
659 views

DirectX11 - Color Interpolation Along Quad Diagonal

Imagine that we have a vertex structure that looks like this: struct Vertex { XMFLOAT3 position; XMFLOAT4 color; }; The vertex shader looks like this: <...
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4 votes
1 answer
2k views

equirectangular panorama rendering?

I want to render my scenes as equirectangular panorama frames. I can get the angular fisheye which is what I actually need by applying the rendered frame as a texture to a correctly UV mapped circle. ...
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  • 141
4 votes
1 answer
5k views

How to generate a RGB * a texture for a glow effect in GLSL?

I would like to create a glow effect in GLSL, there is a tutorial that explains how we multiply RGB * a : I have some questions : is it an operation that is in a fragment shader, where RGBa is ...
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  • 679
4 votes
1 answer
3k views

Infinite world floor grid shader

I am trying to render an infinite world floor grid, similar to this question. My project is using SceneKit with Metal Shading Language but the concepts are no doubt similar between GLSL/HLSL. Here is ...
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  • 1,379
4 votes
2 answers
1k views

How do I get a Light's Range value in Shader?

I'm trying to write a simple frag/vert shader that, depending on whether it is in the range of a light, will paint the appropriate colour from either the 'lit' texture or from the 'unlit' texture. ...
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4 votes
1 answer
1k views

Getting rid of texture bleeding

Edit: I figured out what problem I was facing, it's called Texture/Pixel bleeding, which I was not aware of yet. I posted an answer below consisting of a small description of the problem and a link to ...
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  • 1,507
4 votes
1 answer
4k views

Two pass blur shader using libgdx tile map renderer

I am trying to apply the following technique: blur effect using two pass shader to my libgdx game using the OrthogonalTiledMapRenderer. The idea is to blur the background wich is also a tilemap but ...
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4 votes
0 answers
147 views

Writing a leather shader

I'm trying to write a leather material shader. I have a normal map, bump map (grayscaled), specular map, diffuse map, cube maps. I have done the following ...
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4 votes
0 answers
2k views

How do I sample a cubic shadow map in DirectX 11?

I've implemented a cubic shadow map for dealing with omni-directional light sources in my scene. By defualt it produces hard shadows Obviously a shadow map with higher resolution (currently using ...
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  • 215
4 votes
1 answer
628 views

Fog shader camera problem

I have some difficulties with my vertex-fragment fog shader in Unity. I have a good visual result but the problem is that the gradient is based on the camera's position, it moves as the camera moves. ...
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  • 1,045
3 votes
3 answers
4k views

How to prevent intepolated texture in fragment shader (Unity CG)

Think about minecraft - all the textures in minecraft have a very nice crisp pixelated look. Well, I'm trying to write a shader that will do this but it appears "sampler2d" returns some sort of ...
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3 votes
1 answer
6k views

Depth Intersection Shader

I am trying to create a shader in Unity that shows where intersections occur between objects. Most of the shader I have so far is based off of this youtube tutorial. However, I have made some slight ...
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  • 175
3 votes
1 answer
163 views

Super formula on shader

I'm using Shader-toy to experiment and try to learn a bit the shader science. As exercise I wan to replicate some of the wikipedia math plots. I've started with a Super Formula. What I want to ...
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