Shader programming: where to start?

[niektb]

Hello guys,

I fancy programming some GLSL shaders in 0 A.D. but I don't know where to start.

I checked the wiki but not much info was posted there.

Which program should I use to create them and which version of GLSL is used in 0 A.D.?

Do I need other stuff?

Regards,

Niek

[sanderd17]

For such questions, it's best to come on the #0ad-dev irc channel on Quakenet. People like Philip and historicbruno probably know everything about it.

[ProvencalLeGaullois]

If you are using OpenGL :

OpenGL Shading Language "the orange book".

It seems you can download for free the second edition, if your not to far of an university you can look at their math/computer library, mine have the book...

nvidia GPU gems are often cited to have some good examples. Also you canf ound some publications about some shaders... I am myself learning and writing an opengl application using shaders, so if you have some good resources plz share it

[historic_bruno]

A few 0 A.D.-specific resources to get you started:

0 A.D. Modding Guide - explains about modding the game and mentions some popular tools

Material system - technical details about the game's shader and material system, including what versions we use. No doubt it won't answer every question, then you'll have to delve into the engine source code or ask someone

Personally, I'm on Windows most of the time, and I just use Notepad++ to modify the shaders. A tool that can be priceless in debugging your work is gDEBugger.

[niektb]

I noticed on the fly that we still use OpenGL 2.1. Why don't we use a newer version like 4.2?

[wraitii]

4.2 is not supported by every graphic card (faaaar from it, actually), 2.1 is a version that is, on the other hand, pretty universally supported.

[niektb]

Any tools to display the result quickly? I used Shader Designer, but it seems to me that these shaders won't work in the game.

[ProvencalLeGaullois]

there is some software for shaders dev. Saddly (for me) most of them are written for windows... I read some time that RenderMonkey (ATI) is a very good software. I never used RenderMonkey, I don't know if it's still up to date or not, if it's good for opengl and/or directx... When I tried for myself to found a software, I found some other (on sourceforge iirc) who looked interesting but all for windows... So I'm writing my own application, it will never as good as RenderMonkey or such (so far).... but it will enough for my needs.

[niektb]

Rendermonkey is EOL. Last release was in 2008. But I just came across OpenSceneGraph, which looks very interesting.

http://www.openscenegraph.org/

It is fully cross-platform and it looks like being maintained and used. Plenty of resources as well.

[ProvencalLeGaullois]

I'm using openscenegraph too. Saddly most of the documentation on the web are outdated, there is two books I have them at university. You have to use the mailling list to get some help. OSG is a 3D engine, so you can use shaders and write a program, but there is no tools for shaders dev (for what I know). OSG is used for virtual environment, not for games. The reason of why is not use in games isn't really clear for me, some peoples say scene graph is not good for games, but I read one time that was true ~20 years ago but not anymore today. If you are looking for a 3D engine which use a lot shaders (with opengl) peek a look at Horde3D.

(hope my english isn't too crappy because I'm tired)

edit :: when I send to the OSG mailling list a mail about the lack of documentation, they told me to study the examples who come with OSG.

Edited December 28, 2013 by ProvencalLeGaullois

[feneur]

Any tools to display the result quickly? I used Shader Designer, but it seems to me that these shaders won't work in the game.

Actually you shouldn't need to use a specific tool just to display it, Pyrogenesis should automatically detect that a file has been changed and update the display. Just open up Atlas and add an object using the shader you're working on and save the file when you want to see the result.

[niektb]

I tried to implement a simple post-proc shader but nothing happened at all in the Atlas! Even the other shaders didn't change anything. (I'm sorry. I'm unable to upload my shader due to permission restrictions.)

[sanderd17]

Did you try in game too? Some options are disabled in Atlas.

[feneur]

I tried to implement a simple post-proc shader but nothing happened at all in the Atlas! Even the other shaders didn't change anything. (I'm sorry. I'm unable to upload my shader due to permission restrictions.)

We could enable more file formats, but I'm generally against it - it's better if people put their files in ZIPs/7zips/GZs/some compressed format as that takes up less space on the servers/is quicker for people to download

[Josh]

AMD CodeXL is a nice Linux/Windows debugging tool.

[niektb]

Though I pick my own PostProc effect, the xml-file says that the default is selected. Same for other effects.

Edited December 30, 2013 by niektb

[niektb]

It took a while before I started again on programming shaders.

This time I tried creating a FXAA-shader. No luck however:

Does anybody has some thoughts on this?

I tried modifying the following shader:

https://code.google.com/p/processing/source/browse/trunk/processing/java/libraries/opengl/examples/Shaders/FXAA/data/fxaa.glsl?r=9668

Some background information on FXAA:

http://developer.download.nvidia.com/assets/gamedev/files/sdk/11/FXAA_WhitePaper.pdf

The code:

fxaa.xml

<?xml version="1.0" encoding="utf-8"?><program type="glsl">    <vertex file="glsl/hdr.vs">        <stream name="pos"/>        <stream name="uv0"/>        <attrib name="a_vertex" semantics="gl_Vertex"/>        <attrib name="a_uv0" semantics="gl_MultiTexCoord0"/>    </vertex>    <fragment file="glsl/fxaa.fs"/></program>

fxaa.fs

#version 120uniform sampler2D renderedTex;varying vec2 v_tex;void main() {  // The parameters are hardcoded for now, but could be  // made into uniforms to control fromt he program.  float FXAA_SPAN_MAX = 8.0;  float FXAA_REDUCE_MUL = 1.0/8.0;  float FXAA_REDUCE_MIN = (1.0/128.0);  vec3 rgbNW = texture2D(renderedTex, v_tex + (vec2(-1.0, -1.0) )).rgb;  vec3 rgbNE = texture2D(renderedTex, v_tex + (vec2(+1.0, -1.0))).rgb;  vec3 rgbSW = texture2D(renderedTex, v_tex + (vec2(-1.0, +1.0))).rgb;  vec3 rgbSE = texture2D(renderedTex, v_tex + (vec2(+1.0, +1.0))).rgb;  vec3 rgbM  = texture2D(renderedTex, v_tex).rgb;	  vec3 luma = vec3(0.299, 0.587, 0.114);  float lumaNW = dot(rgbNW, luma);  float lumaNE = dot(rgbNE, luma);  float lumaSW = dot(rgbSW, luma);  float lumaSE = dot(rgbSE, luma);  float lumaM  = dot( rgbM, luma);	  float lumaMin = min(lumaM, min(min(lumaNW, lumaNE), min(lumaSW, lumaSE)));  float lumaMax = max(lumaM, max(max(lumaNW, lumaNE), max(lumaSW, lumaSE)));	  vec2 dir;  dir.x = -((lumaNW + lumaNE) - (lumaSW + lumaSE));  dir.y =  ((lumaNW + lumaSW) - (lumaNE + lumaSE));	  float dirReduce = max((lumaNW + lumaNE + lumaSW + lumaSE) * (0.25 * FXAA_REDUCE_MUL), FXAA_REDUCE_MIN);	    float rcpDirMin = 1.0/(min(abs(dir.x), abs(dir.y)) + dirReduce);	  dir = min(vec2(FXAA_SPAN_MAX,  FXAA_SPAN_MAX),         max(vec2(-FXAA_SPAN_MAX, -FXAA_SPAN_MAX), dir * rcpDirMin));		  vec3 rgbA = (1.0/2.0) * (              texture2D(renderedTex, v_tex + dir * (1.0/3.0 - 0.5)).rgb +              texture2D(renderedTex, v_tex + dir * (2.0/3.0 - 0.5)).rgb);  vec3 rgbB = rgbA * (1.0/2.0) + (1.0/4.0) * (              texture2D(renderedTex, v_tex + dir * (0.0/3.0 - 0.5)).rgb +              texture2D(renderedTex, v_tex + dir * (3.0/3.0 - 0.5)).rgb);  float lumaB = dot(rgbB, luma);  if((lumaB < lumaMin) || (lumaB > lumaMax)){    gl_FragColor.rgb=rgbA;  } else {    gl_FragColor.rgb=rgbB;  }  gl_FragColor.a = 1.0;}

fxaa.zip

fxaa.zip

Edited January 29, 2014 by niektb

[niektb]

An interesting announcement:

http://richg42.blogspot.nl/2014/01/vogl-opengl-tracerdebugger-bonus-content.html?showComment=1389950449081#c343074267754586249

Valve has released a OpenGL debugger for Linux and made it opensource:

https://github.com/ValveSoftware/vogl

[Stan`]

Did you make any improvement on your shader ?

[niektb]

Did you make any improvement on your shader ?

No, my latest result was the first image you encounter when you scroll to the top. It discouraged me to go any further. The problem is that I have no idea what input I get from the engine and what I should send back.

[Stan`]

Maybe Iron Nerd may help you is starting to get involved in graphical programmation stuff ?