/**
** Supermodel
** A Sega Model 3 Arcade Emulator.
** Copyright 2011 Bart Trzynadlowski, Nik Henson
**
** This file is part of Supermodel.
**
** Supermodel is free software: you can redistribute it and/or modify it under
** the terms of the GNU General Public License as published by the Free
** Software Foundation, either version 3 of the License, or (at your option)
** any later version.
**
** Supermodel is distributed in the hope that it will be useful, but WITHOUT
** ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
** FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
** more details.
**
** You should have received a copy of the GNU General Public License along
** with Supermodel. If not, see <http://www.gnu.org/licenses/>.
**/
/*
* Fragment.glsl
*
* Fragment shader for 3D rendering.
*/
#version 120
// Global uniforms
uniform sampler2D textureMap; // complete texture map, 2048x2048 texels
uniform vec4 spotEllipse; // spotlight ellipse position: .x=X position (screen coordinates), .y=Y position, .z=half-width, .w=half-height)
uniform vec2 spotRange; // spotlight Z range: .x=start (viewspace coordinates), .y=limit
uniform vec3 spotColor; // spotlight RGB color
// Inputs from vertex shader
varying vec4 fsSubTexture; // .x=texture X, .y=texture Y, .z=texture width, .w=texture height (all in texels)
varying vec4 fsTexParams; // .x=texture enable (if 1, else 0), .y=use transparency (if > 0), .z=U wrap mode (1=mirror, 0=repeat), .w=V wrap mode
varying float fsTexFormat; // .x=T1RGB5 contour texture (if > 0)
varying float fsTransLevel; // translucence level, 0.0 (transparent) to 1.0 (opaque)
varying vec3 fsLightIntensity; // lighting intensity
varying float fsFogFactor; // fog factor
varying float fsViewZ; // Z distance to fragment from viewpoint at origin
/*
* WrapTexelCoords():
*
* Computes the normalized OpenGL S,T coordinates within the 2048x2048 texture
* sheet, taking into account wrapping behavior.
*
* Computing normalized OpenGL texture coordinates (0 to 1) within the
* Real3D texture sheet:
*
* If the texture is not mirrored, we simply have to clamp the
* coordinates to fit within the texture dimensions, add the texture
* X, Y position to select the appropriate one, and normalize by 2048
* (the dimensions of the Real3D texture sheet).
*
* = [(u,v)%(w,h)+(x,y)]/(2048,2048)
*
* If mirroring is enabled, textures are mirrored every odd multiple of
* the original texture. To detect whether we are in an odd multiple,
* simply divide the coordinate by the texture dimension and check
* whether the result is odd. Then, clamp the coordinates as before but
* subtract from the last texel to mirror them:
*
* = [M*((w-1,h-1)-(u,v)%(w,h)) + (1-M)*(u,v)%(w,h) + (x,y)]/(2048,2048)
* where M is 1.0 if the texture must be mirrored.
*
* As an optimization, this function computes TWO texture coordinates
* simultaneously. The first is texCoord.xy, the second is in .zw. The other
* parameters must have .xy = .zw.
*/
vec4 WrapTexelCoords(vec4 texCoord, vec4 texOffset, vec4 texSize, vec4 mirrorEnable)
{
vec4 clampedCoord, mirror, glTexCoord;
clampedCoord = mod(texCoord,texSize); // clamp coordinates to within texture size
mirror = mirrorEnable * mod(floor(texCoord/texSize),2.0); // whether this texel needs to be mirrored
glTexCoord = ( mirror*(texSize-clampedCoord) +
(vec4(1.0,1.0,1.0,1.0)-mirror)*clampedCoord +
texOffset
) / 2048.0;
/*
glTexCoord = ( mirror*(texSize-vec4(1.0,1.0,1.0,1.0)-clampedCoord) +
(vec4(1.0,1.0,1.0,1.0)-mirror)*clampedCoord +
texOffset
) / 2048.0;
*/
return glTexCoord;
}
/*
* main():
*
* Fragment shader entry point.
*/
void main(void)
{
vec4 uv_top, uv_bot, c[4];
vec2 r;
vec4 fragColor;
vec2 ellipse;
vec3 lightIntensity;
float insideSpot;
// Get polygon color for untextured polygons (textured polygons will overwrite)
if (fsTexParams.x==0.0)
fragColor = gl_Color;
else
// Textured polygons: set fragment color to texel value
{
/*
* Bilinear Filtering
*
* In order to get this working on ATI, the number of operations is
* reduced by putting everything into vec4s. uv_top holds the UV
* coordinates for the top two texels (.xy=left, .zw=right) and uv_bot
* is for the lower two.
*/
// Compute fractional blending factor, r, and lower left corner of texel 0
uv_bot.xy = gl_TexCoord[0].st-vec2(0.5,0.5); // move into the lower left blending texel
r = uv_bot.xy-floor(uv_bot.xy); // fractional part
uv_bot.xy = floor(uv_bot.xy); // integral part
// Compute texel coordinates
uv_bot.xy += vec2(0.5,0.5); // offset to center of pixel (should not be needed but it fixes a lot of glitches, esp. on Nvidia)
uv_bot.zw = uv_bot.xy + vec2(1.0,0.0); // compute coordinates of the other three neighbors
uv_top = uv_bot + vec4(0.0,1.0,0.0,1.0);
// Compute the properly wrapped texel coordinates
uv_top = WrapTexelCoords(uv_top,vec4(fsSubTexture.xy,fsSubTexture.xy),vec4(fsSubTexture.zw,fsSubTexture.zw), vec4(fsTexParams.zw,fsTexParams.zw));
uv_bot = WrapTexelCoords(uv_bot,vec4(fsSubTexture.xy,fsSubTexture.xy),vec4(fsSubTexture.zw,fsSubTexture.zw), vec4(fsTexParams.zw,fsTexParams.zw));
// Fetch the texels
c[0]=texture2D(textureMap,uv_bot.xy); // bottom-left (base texel)
c[1]=texture2D(textureMap,uv_bot.zw); // bottom-right
c[2]=texture2D(textureMap,uv_top.xy); // top-left
c[3]=texture2D(textureMap,uv_top.zw); // top-right
// Interpolate texels and blend result with material color to determine final (unlit) fragment color
// fragColor = (c[0]*(1.0-r.s)*(1.0-r.t) + c[1]*r.s*(1.0-r.t) + c[2]*(1.0-r.s)*r.t + c[3]*r.s*r.t);
// Faster method:
c[0] += (c[1]-c[0])*r.s; // 2 alu
c[2] += (c[3]-c[2])*r.s; // 2 alu
fragColor = c[0]+(c[2]-c[0])*r.t; //2 alu
/*
* T1RGB5:
*
* The transparency bit determines whether to discard pixels (if set).
* What is unknown is how this bit behaves when interpolated. OpenGL
* processes it as an alpha value, so it might concievably be blended
* with neighbors. Here, an arbitrary threshold is chosen.
*
* To-do: blending could probably enabled and this would work even
* better with a hard threshold.
*
* Countour processing also seems to be enabled for RGBA4 textures.
* When the alpha value is 0.0 (or close), pixels are discarded
* entirely.
*/
if (fsTexParams.y > 0.0) // contour processing enabled
{
if (fragColor.a < 0.01) // discard anything with alpha == 0
discard;
}
// If contour texture and not discarded, force alpha to 1.0 because will later be modified by polygon translucency
if (fsTexFormat > 0.0) // contour (T1RGB5) texture map
fragColor.a = 1.0;
}
// Compute spotlight and apply lighting
ellipse = (gl_FragCoord.xy-spotEllipse.xy)/spotEllipse.zw;
insideSpot = dot(ellipse,ellipse);
if ((insideSpot <= 1.0) && (fsViewZ>=spotRange.x) && (fsViewZ<spotRange.y))
lightIntensity = fsLightIntensity+(1.0-insideSpot)*spotColor;
else
lightIntensity = fsLightIntensity;
fragColor.rgb *= lightIntensity;
// Translucency (modulates existing alpha channel for RGBA4 texels)
fragColor.a *= fsTransLevel;
// Apply fog under the control of fog factor setting from polygon header
fragColor.rgb = mix(gl_Fog.color.rgb, fragColor.rgb, fsFogFactor );
// Store final color
gl_FragColor = fragColor;
}