q3rally/engine/docs/opengl2-readme.md

OpenGL2

OpenGL2 is an alternate renderer for ioquake3. It aims to implement modern features and technologies into the id tech 3 engine, but without sacrificing compatibility with existing Quake 3 mods.

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FEATURES

• Compatible with most vanilla Quake 3 mods.
• HDR Rendering, and support for HDR lightmaps
• Tone mapping and auto-exposure.
• Cascaded shadow maps.
• Multisample anti-aliasing.
• Texture upsampling.
• Advanced materials support.
• Advanced shading and specular methods.
• RGTC and BPTC texture compression support.
• Screen-space ambient occlusion.

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INSTALLATION

For *nix:

1. This should be identical to installing ioq3. Check their README for more details.

For Win32:

1. Have a Quake 3 install, fully patched.

2. Copy the following files into Quake 3's install directory:

   ioquake3.x86.exe renderer_opengl1_x86.dll renderer_opengl2_x86.dll

   These can be found in build/release-mingw32-x86 after compiling, or bug someone to release binaries.

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RUNNING

1. Start ioquake3. (ioquake3.x86.exe on Win32)

2. Open the console (the default key is tilde ~) and type /cl_renderer opengl2 and press enter /vid_restart then press enter again.

3. Enjoy.

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CVARS

Cvars for simple rendering features:

• r_ext_compressed_textures - Automatically compress textures. 0 - No texture compression. (default) 1 - DXT/RGTC texture compression if supported. 2 - BPTC texture compression if supported.

• r_ext_framebuffer_multisample - Multisample Anti-aliasing. 0 - None. (default) 1-16 - Some. 17+ - Too much!

• r_ssao - Enable screen-space ambient occlusion. Currently eats framerate and has some visible artifacts. 0 - No. (default) 1 - Yes.

Cvars for HDR and tonemapping:

• r_hdr - Do scene rendering in a framebuffer with high dynamic range. (Less banding, and exposure changes look much better) 0 - No. 1 - Yes. (default)

• r_cameraExposure - Cheat. Alter brightness, in powers of two. -2 - 4x as dark. 0 - Normal. (default) 0.5 - Sqrt(2)x as bright. 2 - 4x as bright.

• r_postProcess - Enable post-processing. 0 - No. 1 - Yes. (default)

• r_toneMap - Enable tone mapping. Requires r_hdr and r_postProcess. 0 - No. 1 - Yes. (default)

• r_forceToneMap - Cheat. Override built-in and map tonemap settings and use cvars r_forceToneMapAvg, r_forceToneMapMin, and r_forceToneMapMax. 0 - No. (default) 1 - Yes.

• r_forceToneMapAvg - Cheat. Map average scene luminance to this value, in powers of two. Requires r_forceToneMap. -2.0 - Dark. -1.0 - Kinda dark. (default). 2.0 - Too bright.

• r_forceToneMapMin - Cheat. After mapping average, luminance below this level is mapped to black. Requires r_forceToneMap. -5 - Not noticeable. -3.25 - Normal. (default) 0.0 - Too dark.

• r_forceToneMapMin - Cheat. After mapping average, luminance above this level is mapped to white. Requires r_forceToneMap. 0.0 - Too bright. 1.0 - Normal. (default). 2.0 - Washed out.

• r_autoExposure - Do automatic exposure based on scene brightness. Hardcoded to -2 to 2 on maps that don't specify otherwise. Requires r_hdr, r_postprocess, and r_toneMap. 0 - No. 1 - Yes. (default)

• r_forceAutoExposure - Cheat. Override built-in and map auto exposure settings and use cvars r_forceAutoExposureMin and r_forceAutoExposureMax. 0 - No. (default) 1 - Yes.

• r_forceAutoExposureMin - Cheat. Set minimum exposure to this value, in powers of two. Requires r_forceAutoExpsure. -3.0 - Dimmer. -2.0 - Normal. (default) -1.0 - Brighter.

• r_forceAutoExposureMax - Cheat. Set maximum exposure to this value, in powers of two. Requires r_forceAutoExpsure. 1.0 - Dimmer. 2.0 - Normal. (default) 3.0 - Brighter.

Cvars for advanced material usage:

• r_normalMapping - Enable normal maps for materials that support it. 0 - No. 1 - Yes. (default)

• r_specularMapping - Enable specular maps for materials that support it. 0 - No. 1 - Yes. (default)

• r_deluxeMapping - Enable deluxe mapping. (Map is compiled with light directions.) Even if the map doesn't have deluxe mapping compiled in, an approximation based on the lightgrid will be used. 0 - No. 1 - Yes. (default)

• r_parallaxMapping - Enable parallax mapping for materials that support it. 0 - No. (default) 1 - Use parallax occlusion mapping. 2 - Use relief mapping. (slower)

• r_parallaxMapOffset - Set the parallax height offset. 0 - Values map to -255 - 0. (default) 0.5 - Values map to -127 - 127. 1.0 - Values map to 0 - 255.

• r_parallaxMapShadows - Enable self-shadowing on parallax map supported materials. 0 - No. (default) 1 - Yes.

• r_baseSpecular - Set the specular reflectance of materials which don't include a specular map or use the specularReflectance keyword. 0 - No. 0.04 - Realistic. (default) 1.0 - Ack.

• r_baseGloss - Set the glossiness of materials which don't include a specular map or use the specularExponent keyword. 0 - Rough. 0.3 - Default. 1.0 - Shiny.

• r_baseNormalX - Set the scale of the X values from normal maps when the normalScale keyword is not used. -1 - Flip X. 0 - Ignore X. 1 - Normal X. (default) 2 - Double X.

• r_baseNormalY - Set the scale of the Y values from normal maps when the normalScale keyword is not used. -1 - Flip Y. 0 - Ignore Y. 1 - Normal Y. (default) 2 - Double Y.

• r_baseParallax - Sets the scale of the parallax effect for materials when the parallaxDepth keyword is not used. 0 - No depth. 0.01 - Pretty smooth. 0.05 - Standard depth. (default) 0.1 - Looks broken.

• r_pbr - Enable physically based rendering. Experimental, will not look correct without assets meant for it. 0 - No. (default) 1 - Yes.

Cvars for image interpolation and generation:

• r_imageUpsample - Use interpolation to artificially increase the resolution of all textures. Looks good in certain circumstances. 0 - No. (default) 1 - 2x size. 2 - 4x size. 3 - 8x size, etc

• r_imageUpsampleMaxSize - Maximum texture size when upsampling textures. 1024 - Default. 2048 - Really nice. 4096 - Really slow. 8192 - Crash.

• r_imageUpsampleType - Type of interpolation when upsampling textures. 0 - None. (probably broken) 1 - Bad but fast (default, FCBI without second derivatives) 2 - Okay but slow (normal FCBI)

• r_genNormalMaps - Naively generate normal maps for all textures. 0 - Don't. (default) 1 - Do.

Cvars for the sunlight and cascaded shadow maps:

• r_forceSun - Cheat. Force sunlight and shadows, using sun position from sky material. 0 - Don't. (default) 1 - Do. 2 - Sunrise, sunset.

• r_forceSunLightScale - Cheat. Scale sun brightness by this factor when r_forceSun 1. 1.0 - Default

• r_forceSunAmbientScale - Cheat. Scale sun ambient brightness by this factor when r_forceSun 1. 0.5 - Default

• r_sunShadows - Enable sunlight and cascaded shadow maps for it on maps that support it. 0 - No. 1 - Yes. (default)

• r_sunlightMode - Specify the method used to add sunlight to the scene. 0 - No. 1 - Multiply lit areas by light scale, and shadowed areas by ambient scale. (default) 2 - Add light. Looks better, but is slower and doesn't integrate well with existing maps.

• r_shadowFilter - Enable filtering shadows for a smoother look. 0 - No. 1 - Some. (default) 2 - Much.

• r_shadowMapSize - Size of each cascaded shadow map. 256 - 256x256, ugly, probably shouldn't go below this. 512 - 512x512, passable. 1024 - 1024x1024, good. (default) 2048 - 2048x2048, extreme. 4096 - 4096x4096, indistinguishable from 2048.

Cvars that you probably don't care about or shouldn't mess with:

• r_depthPrepass - Do a depth-only pass before rendering. Speeds up rendering in cases where advanced features are used. Required for r_sunShadows. 0 - No. 1 - Yes. (default)

• r_mergeLightmaps - Merge the small (128x128) lightmaps into 2 or fewer giant (4096x4096) lightmaps. Easy speedup. 0 - Don't. 1 - Do. (default)

• r_shadowCascadeZNear - Near plane for shadow cascade frustums. 4 - Default.

• r_shadowCascadeZFar - Far plane for shadow cascade frustums. 3072 - Default.

• r_shadowCascadeZBias - Z-bias for shadow cascade frustums. -256 - Default.

Cvars that have broken bits:

• r_dlightMode - Change how dynamic lights look. 0 - Quake 3 style dlights, fake brightening. (default) 1 - Actual lighting, no shadows. 2 - Light and shadows. (broken)

• r_pshadowDist - Virtual camera distance when creating shadowmaps for projected shadows. Deprecated.

• cg_shadows - Old shadow code. Deprecated.

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MATERIALS

OpenGL2 supports .mtr files, which are basically the same as .shader files, and are located in the same place, but override existing .shader files if they exist. This is to allow maps and mods to use the new material features without breaking the map when using the old renderer.

Here's an example of a material stored in one, showing off some new features:

textures/abandon/grass
{
    qer_editorimage textures/abandon/grass.jpg
    {
        map textures/abandon/grass3_256_d.jpg
        rgbgen identity
    }
    {
        stage normalparallaxmap
        map textures/abandon/grass3_1024_n.png
        normalScale 1 1
        parallaxDepth 0.05
    }
    {
        stage specularmap
        map textures/abandon/grass3_256_s.png
        specularReflectance 0.12
        specularExponent 16
    }
    {
        map $lightmap
        blendfunc GL_DST_COLOR GL_ZERO
    }
}

The first thing to notice is that this is basically the same as old Quake 3 shader files. The next thing to notice are the new keywords. Here is what they mean:

stage <type> - State how this imagemap will be used by OpenGL2: diffuseMap - Standard, same as no stage entry normalMap - Image will be used as a normal map normalParallaxMap - Image will be used as a normal map with alpha treated as height for parallax mapping specularMap - Image will be used as a specular map with alpha treated as shininess.

specularReflectance <value> - State how metallic this material is. Metals typically have a high specular and a low diffuse, so this is typically high for them, and low for other materials, such as plastic. For typical values for various materials, see http://refractiveindex.info , pick a material, then scroll down to the reflection calculator and look up its reflectance. Default is 0.04, since most materials aren't metallic.

specularExponent <value> - State how shiny this material is. Note that this is modulated by the alpha channel of the specular map, so if it were set to 16, and the alpha channel of the specular map was set to 0.5, then the shininess would be set to 8. Default 256.

normalScale <x> <y> - State the X and Y scales of the normal map. This is useful for increasing or decreasing the "strength" of the normal map, or entering negative values to flip the X and/or Y values. Default 1 1.

parallaxDepth <value> - State the maximum depth of the parallax map. This is a fairly sensitive value, and I recommend the default or lower. Default 0.05.

An important note is that normal and specular maps influence the diffuse map declared before them, so materials like this are possible:

textures/terrain/grass
{
    qer_editorimage textures/terrain/grass.jpg

    {
        map textures/terrain/rock.jpg
    }
    {
        stage normalparallaxmap
        map textures/terrain/rock_n.png
    }
    {
        stage specularmap
        map textures/terrain/rock_s.jpg
    }
    {
        map textures/terrain/grass.jpg
        blendFunc GL_SRC_ALPHA GL_ONE_MINUS_SRC_ALPHA
        alphaGen vertex
    }
    {
        stage normalparallaxmap
        map textures/terrain/grass_n.png
    }
    {
        stage specularmap
        map textures/terrain/grass_s.png
        specularReflectance 0.12
    }
    {
        map $lightmap
        blendfunc GL_DST_COLOR GL_ZERO
    }
}

Though note due to the complexity of lighting, dynamic light (including sunlight with cascaded shadow maps) currently only works 100% on materials like this, where the second diffuse map doesn't have its own alpha, and only uses vertex alpha. YMMV.

Another addition to materials is working normal/specular maps on vertex lit surfaces. To enable this, make your material look like this:

textures/vehicles/car
{
    qer_editorimage textures/vehicles/car.jpg

    {
        map textures/vehicles/car.jpg
        rgbGen vertexLit
    }
    {
        stage normalparallaxmap
        map textures/vehicles/car_n.jpg
    }
    {
        stage specularmap
        map textures/vehicles/car_s.jpg
    }
}

Note the new keyword, 'vertexLit' after rgbGen. This is analogous to 'rgbGen vertex', except a light direction will be determined from the lightgrid and used with the normal and specular maps. 'exactVertexLit' exists as well, and is the equivalent for 'exactVertex'.

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DYNAMIC SUNLIGHT AND CASCADED SHADOW MAPS

This adds a new keyword to sky materials, q3gl2_sun. The syntax is:

q3gl2_sun <red> <green> <blue> <intensity> <degrees> <elevation> <shadowScale>

Note the first six parameters are the same as in q3map_sun or q3map_sunExt, and the last two indicate scaling factors for the map brightness and an ambient light of the same color as the sun.

There are currently two ways to use this in your own (and other people's) maps.

1. Create your map as normal, set r_sunlightMode to 1, and add a 'q3gl2_sun' line after your 'q3map_sun' line in your sky material, like so:

   textures/skies/bluesky { qer_editorimage textures/skies/bluesky.jpg

    surfaceparm nomarks
    surfaceparm noimpact
    surfaceparm nolightmap
    surfaceparm sky
    q3map_sunExt 240 238 200 100 195 35 3 16
    q3gl2_sun 240 238 200 50 195 35 0.2
    q3map_skylight 50 16
    q3map_lightimage $whiteimage
   
    skyparms env/bluesky - -
   

   }

   The advantages with this method are that your map will continue to work with the old renderer with the sunlight baked into the lightmap, and it can be used with existing maps without recompilation. The downside is artifacts like doubled shadows and uneven shadow edges.

2. Set r_sunlightMode to 2 and use 'q3gl2_sun' instead of 'q3map_sun' or 'q3map_sunExt', like so:

   textures/skies/bluesky { qer_editorimage textures/skies/bluesky.jpg

    surfaceparm nomarks
    surfaceparm noimpact
    surfaceparm nolightmap
    surfaceparm sky
    q3gl2_sun 240 238 200 50 195 35 0.2
    q3map_skylight 50 16
    q3map_lightimage $whiteimage
   
    skyparms env/bluesky - -
   

   }

   The advantages with this method are that you don't get the artifacts that characterize the other method, and your map compiles a lot faster without the sunlight bouncing calculations. The downsides are that your map will not display properly with the old renderer, and you lose the bounced light that compiling the map with q3map_sun* in it would have.

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TONE MAPPING AND AUTO EXPOSURE

This adds a new keyword to sky materials, q3gl2_tonemap. The syntax is:

q3gl2_tonemap <toneMapMin> <toneMapAvg> <toneMapMax> <autoExposureMin> <autoExposureMax>

Each of these settings corresponds to a matching cvar, so you can view and adjust the effect before settling on fixed settings.

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THANKS

I'd like to take this part of the readme to thank the numerous people who contributed thoughts, ideas, and whole swaths of code to this project.

• Id Software, for creating Quake 3 and releasing its source code under a GPL license, without which this project would not be possible.

• Zachary 'Zakk' Slater, Thilo Schulz, Tim Angus, and the rest of the ioquake3 team and contributors, for improving massively upon the raw Quake 3 source, and accepting my and gimhael's modular renderer patch.

• Robert 'Tr3B' Beckebans and the other contributors to XReaL, for letting me liberally copy code from you. :)

• Andrew 'Black Monk' Prosnik, Andrei 'Makro' Drexler, Tomi 'T.T.I.' Isoaho, Richard 'JBravo' Allen, Walter 'Johnny Rocket' Somol, and the rest of the Boomstick Studios, for contributing code, feature requests, and testing.

• Yoshiharu Gotanda, Tatsuya Shoji, and the rest of tri-Ace's R&D Department, for creating the tri-Ace shading equations and posting their derivations in simple English.

• Matthias 'gimhael' Bentrup, for random ideas and bits of code.

• Evan 'megatog615' Goers, for testing, ideas, and bugging me just enough that I'd write documentation. :)

• The folks at #ioquake3, who don't seem to mind when I suddenly drop a screenshot and insist on talking about it. :)

• And lots of various other random people, who posted on forums, blogs, and Wikipedia, who helped in small but numerous ways.

If I missed you in this section, feel free to drop me a line and I'll add you.

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CONTACT

My name is James Canete, and I wrote most of this readme. Also, a renderer.

If you wish to get in touch with me, try my GMail at use.less01 (you should be able to solve this), or look for SmileTheory in #ioquake3 on irc.freenode.net.