From 4085a9d97e2e54e277b26c7a7317bd4c12f4528e Mon Sep 17 00:00:00 2001
From: Chris Laurel <claurel@gmail.com>
Date: Wed, 28 Feb 2001 02:49:35 +0000
Subject: [PATCH] Functions for setting up the nVidia register combiners.

---
 src/regcombine.cpp | 94 ++++++++++++++++++++++++++++++++++++++++++++++
 src/regcombine.h   | 23 ++++++++++++
 2 files changed, 117 insertions(+)
 create mode 100644 src/regcombine.cpp
 create mode 100644 src/regcombine.h

diff --git a/src/regcombine.cpp b/src/regcombine.cpp
new file mode 100644
index 00000000..838f878b
--- /dev/null
+++ b/src/regcombine.cpp
@@ -0,0 +1,94 @@
+// regcombine.cpp
+// 
+// Copyright (C) 2001, Chris Laurel <claurel@shatters.net>
+//
+// Some functions for setting up the nVidia register combiners
+// extension for pretty rendering effects.
+//
+// This program 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 2
+// of the License, or (at your option) any later version.
+
+#include "gl.h"
+#include "glext.h"
+#include "regcombine.h"
+
+
+void SetupCombinersBumpMap(CTexture& bumpTexture,
+                           CTexture& normalizationTexture,
+                           float* ambientColor)
+{
+    glEnable(GL_REGISTER_COMBINERS_NV);
+
+    glDisable(GL_LIGHTING);
+    glActiveTextureARB(GL_TEXTURE1_ARB);
+    glEnable(GL_TEXTURE_CUBE_MAP_EXT);
+    glBindTexture(GL_TEXTURE_2D, normalizationTexture.getName());
+
+    glActiveTextureARB(GL_TEXTURE0_ARB);
+    glEnable(GL_TEXTURE_2D);
+    glBindTexture(GL_TEXTURE_2D, bumpTexture.getName());
+
+    // Just a single combiner stage required . . .
+    glCombinerParameteriNV(GL_NUM_GENERAL_COMBINERS_NV, 1);
+
+    glCombinerParameterfvNV(GL_CONSTANT_COLOR0_NV, ambientColor);
+
+    // Compute N dot L in the RGB portion of combiner 0
+    // Load register A with a normal N from the normal map
+    glCombinerInputNV(GL_COMBINER0_NV, GL_RGB,
+                      GL_VARIABLE_A_NV, GL_TEXTURE0_ARB,
+                      GL_EXPAND_NORMAL_NV, GL_RGB);
+
+    // Load register B with the normalized light direction L
+    glCombinerInputNV(GL_COMBINER0_NV, GL_RGB,
+                      GL_VARIABLE_B_NV, GL_TEXTURE1_ARB,
+                      GL_EXPAND_NORMAL_NV, GL_RGB);
+    
+    // Compute N dot L
+    glCombinerOutputNV(GL_COMBINER0_NV, GL_RGB,
+                       GL_SPARE0_NV, GL_DISCARD_NV, GL_DISCARD_NV,
+                       GL_NONE, GL_NONE, GL_TRUE, GL_FALSE, GL_FALSE);
+
+    // Compute the self-shadowing term in the alpha portion of combiner 0
+    // A = 1
+    glCombinerInputNV(GL_COMBINER0_NV, GL_ALPHA, GL_VARIABLE_A_NV,
+                      GL_ZERO, GL_UNSIGNED_INVERT_NV, GL_ALPHA);
+    // B = L.z
+    glCombinerInputNV(GL_COMBINER0_NV, GL_ALPHA, GL_VARIABLE_B_NV,
+                      GL_TEXTURE1_ARB, GL_EXPAND_NORMAL_NV, GL_BLUE);
+    // C = 1
+    glCombinerInputNV(GL_COMBINER0_NV, GL_ALPHA, GL_VARIABLE_C_NV,
+                      GL_ZERO, GL_UNSIGNED_INVERT_NV, GL_ALPHA);
+    // D = L.z
+    glCombinerInputNV(GL_COMBINER0_NV, GL_ALPHA, GL_VARIABLE_D_NV,
+                      GL_TEXTURE1_ARB, GL_EXPAND_NORMAL_NV, GL_BLUE);
+
+    // Create a steep ramp function for self-shadowing
+    // SPARE0 = 4*(A*B+C*D) = 4*(1*L.z + 1*L.z) = 8 * L.z
+    glCombinerOutputNV(GL_COMBINER0_NV, GL_ALPHA,
+                       GL_DISCARD_NV, GL_DISCARD_NV, GL_SPARE0_NV,
+                       GL_SCALE_BY_FOUR_NV, GL_NONE, GL_FALSE, GL_FALSE, GL_FALSE);
+
+    // A = SPARE0_alpha = per-pixel self-shadowing term
+    glFinalCombinerInputNV(GL_VARIABLE_A_NV,
+                           GL_SPARE0_NV, GL_UNSIGNED_IDENTITY_NV, GL_ALPHA);
+    glFinalCombinerInputNV(GL_VARIABLE_B_NV,
+                           GL_SPARE0_NV, GL_UNSIGNED_IDENTITY_NV, GL_RGB);
+    // D = ambient color
+    glFinalCombinerInputNV(GL_VARIABLE_D_NV,
+                           GL_CONSTANT_COLOR0_NV, GL_UNSIGNED_IDENTITY_NV, GL_RGB);
+    // G = diffuse illumination contribution = L dot N
+    glFinalCombinerInputNV(GL_VARIABLE_G_NV,
+                           GL_SPARE0_NV, GL_UNSIGNED_IDENTITY_NV, GL_ALPHA);
+}
+
+
+void DisableCombiners()
+{
+    glDisable(GL_REGISTER_COMBINERS_NV);
+    glActiveTextureARB(GL_TEXTURE1_ARB);
+    glDisable(GL_TEXTURE_CUBE_MAP_EXT);
+    glActiveTextureARB(GL_TEXTURE0_ARB);
+}
diff --git a/src/regcombine.h b/src/regcombine.h
new file mode 100644
index 00000000..ccc503b7
--- /dev/null
+++ b/src/regcombine.h
@@ -0,0 +1,23 @@
+// regcombine.h
+// 
+// Copyright (C) 2001, Chris Laurel <claurel@shatters.net>
+//
+// Some functions for setting up the nVidia register combiners
+// extension for pretty rendering effects.
+//
+// This program 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 2
+// of the License, or (at your option) any later version.
+
+#ifndef _REGCOMBINE_H_
+#define _REGCOMBINE_H_
+
+#include "texture.h"
+
+extern void SetupCombinersBumpMap(CTexture& bumpTexture,
+                                  CTexture& normalizationTexture,
+                                  float* ambientColor);
+extern void DisableCombiners();
+
+#endif // _REGCOMBINE_H_