use subtractive blend equation to support negative v_brightness; support smaller...

[xonotic/darkplaces.git] / gl_draw.c

diff --git a/gl_draw.c b/gl_draw.c
index 705253b00a30810808935160790f2fd6ff89082d..01329fcb8e7eb5263ee96af18b9731f5fd6c585f 100644 (file)
--- a/gl_draw.c
+++ b/gl_draw.c
@@ -2159,6 +2159,36 @@ void R_DrawGamma(void)
        GL_DepthRange(0, 1);
        GL_PolygonOffset(0, 0);
        GL_DepthTest(false);
+
+       // interpretation of brightness and contrast:
+       //   color range := brightness .. (brightness + contrast)
+       // i.e. "c *= contrast; c += brightness"
+       // plausible values for brightness thus range from -contrast to 1
+
+       // apply pre-brightness (subtractive brightness, for where contrast was >= 1)
+       if (vid.support.ext_blend_subtract)
+       {
+               if (v_color_enable.integer)
+               {
+                       c[0] = -v_color_black_r.value / v_color_white_r.value;
+                       c[1] = -v_color_black_g.value / v_color_white_g.value;
+                       c[2] = -v_color_black_b.value / v_color_white_b.value;
+               }
+               else
+                       c[0] = c[1] = c[2] = -v_brightness.value / v_contrast.value;
+               if (c[0] >= 0.01f || c[1] >= 0.01f || c[2] >= 0.01f)
+               {
+                       // need SUBTRACTIVE blending to do this!
+                       GL_BlendEquationSubtract(true);
+                       GL_BlendFunc(GL_ONE, GL_ONE);
+                       GL_Color(c[0], c[1], c[2], 1);
+                       R_Mesh_PrepareVertices_Generic_Arrays(3, blendvertex3f, NULL, NULL);
+                       R_Mesh_Draw(0, 3, 0, 1, polygonelement3i, NULL, 0, polygonelement3s, NULL, 0);
+                       GL_BlendEquationSubtract(false);
+               }
+       }
+
+       // apply contrast
        if (v_color_enable.integer)
        {
                c[0] = v_color_white_r.value;
@@ -2167,17 +2197,32 @@ void R_DrawGamma(void)
        }
        else
                c[0] = c[1] = c[2] = v_contrast.value;
-       if (c[0] >= 1.01f || c[1] >= 1.01f || c[2] >= 1.01f)
+       if (c[0] >= 1.003f || c[1] >= 1.003f || c[2] >= 1.003f)
        {
                GL_BlendFunc(GL_DST_COLOR, GL_ONE);
-               while (c[0] >= 1.01f || c[1] >= 1.01f || c[2] >= 1.01f)
+               while (c[0] >= 1.003f || c[1] >= 1.003f || c[2] >= 1.003f)
                {
-                       GL_Color(c[0] - 1, c[1] - 1, c[2] - 1, 1);
+                       float cc[4];
+                       cc[0] = bound(0, c[0] - 1, 1);
+                       cc[1] = bound(0, c[1] - 1, 1);
+                       cc[2] = bound(0, c[2] - 1, 1);
+                       GL_Color(cc[0], cc[1], cc[2], 1);
                        R_Mesh_PrepareVertices_Generic_Arrays(3, blendvertex3f, NULL, NULL);
                        R_Mesh_Draw(0, 3, 0, 1, polygonelement3i, NULL, 0, polygonelement3s, NULL, 0);
-                       VectorScale(c, 0.5, c);
+                       c[0] /= 1 + cc[0];
+                       c[1] /= 1 + cc[1];
+                       c[2] /= 1 + cc[2];
                }
        }
+       if (c[0] <= 0.997f || c[1] <= 0.997f || c[2] <= 0.997f)
+       {
+               GL_BlendFunc(GL_DST_COLOR, GL_ZERO);
+               GL_Color(c[0], c[1], c[2], 1);
+               R_Mesh_PrepareVertices_Generic_Arrays(3, blendvertex3f, NULL, NULL);
+               R_Mesh_Draw(0, 3, 0, 1, polygonelement3i, NULL, 0, polygonelement3s, NULL, 0);
+       }
+
+       // apply post-brightness (additive brightness, for where contrast was <= 1)
        if (v_color_enable.integer)
        {
                c[0] = v_color_black_r.value;
@@ -2189,7 +2234,7 @@ void R_DrawGamma(void)
        if (c[0] >= 0.01f || c[1] >= 0.01f || c[2] >= 0.01f)
        {
                GL_BlendFunc(GL_ONE, GL_ONE);
-               GL_Color(c[0] - 1, c[1] - 1, c[2] - 1, 1);
+               GL_Color(c[0], c[1], c[2], 1);
                R_Mesh_PrepareVertices_Generic_Arrays(3, blendvertex3f, NULL, NULL);
                R_Mesh_Draw(0, 3, 0, 1, polygonelement3i, NULL, 0, polygonelement3s, NULL, 0);
        }