#5566: Add alphatest support to the z-fill program (WIP)

install/gl/zfill_alpha_fp.glsl

@@ -1,27 +1,25 @@
-/// ============================================================================
-/*
-Copyright (C) 2004 Robert Beckebans <trebor_7@users.sourceforge.net>
-Please see the file "CONTRIBUTORS" for a list of contributors
 
-This program is free software; you can redistribute it and/or
-modify it under the terms of the GNU Lesser General Public License
-as published by the Free Software Foundation; either version 2
-of the License, or (at your option) any later version.
+uniform sampler2D   u_diffuse;
+uniform float       u_alpha_test;
 
-This program 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.
+varying vec2        var_tex_diffuse;
 
-See the GNU Lesser General Public License for more details.
+void main()
+{
+    if (u_alpha_test < 0)
+    {
+        gl_FragColor.a = 1.0;
+        gl_FragColor.rgb = vec3(1.0, 1.0, 0.0);
+    }
+    else
+    {
+        vec4 tex = texture2D(u_diffuse, var_tex_diffuse);
 
-You should have received a copy of the GNU Lesser General Public License
-along with this program; if not, write to the Free Software
-Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
-*/
-/// ============================================================================
+        if (tex.a <= u_alpha_test)
+        {
+            discard;
+        }
 
-void	main()
-{
-	gl_FragColor.a = 1.0;
-	gl_FragColor.rgb = vec3(1.0, 1.0, 0.0);
+        gl_FragColor = tex;
+    }
 }

install/gl/zfill_vp.glsl

@@ -22,13 +22,15 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 
 attribute vec4		attr_TexCoord0;
 
+varying vec2		var_tex_diffuse;
+
 void	main()
 {
 	// transform vertex position into homogenous clip-space
 	gl_Position = ftransform();
 
 	// transform texcoords
-	gl_TexCoord[0] = gl_TextureMatrix[0] * gl_MultiTexCoord0;
+	var_tex_diffuse = (gl_TextureMatrix[0] * attr_TexCoord0).st;
 
 	// assign color
 	gl_FrontColor = gl_Color;

radiantcore/rendersystem/backend/OpenGLShader.cpp

@@ -312,6 +312,7 @@ void OpenGLShader::appendInteractionLayer(const DBSTriplet& triplet)
         alphaTest = triplet.diffuse->getAlphaTest();
     }
 
+#if 0
     // Append a depthfill shader pass if requested (not applicable for
     // alpha-test materials)
     if (triplet.needDepthFill && alphaTest <= 0.0)
@@ -329,15 +330,38 @@ void OpenGLShader::appendInteractionLayer(const DBSTriplet& triplet)
 
         zPass.glProgram = _renderSystem.getGLProgramFactory().getBuiltInProgram("depthFill");
     }
+    else
+#else
+    if (triplet.needDepthFill && triplet.diffuse)
+    {
+        // Create depth-buffer fill pass with alpha test
+        OpenGLState& zPass = appendDefaultPass();
+        zPass.setRenderFlag(RENDER_MASKCOLOUR);
+        zPass.setRenderFlag(RENDER_FILL);
+        zPass.setRenderFlag(RENDER_CULLFACE);
+        zPass.setRenderFlag(RENDER_DEPTHTEST);
+        zPass.setRenderFlag(RENDER_DEPTHWRITE);
+        zPass.setRenderFlag(RENDER_PROGRAM);
+        zPass.setRenderFlag(RENDER_ALPHATEST);
+        zPass.setRenderFlag(RENDER_TEXTURE_2D);
+        zPass.setRenderFlag(RENDER_BUMP);
+        zPass.alphaThreshold = static_cast<GLfloat>(alphaTest);
 
+        zPass.setSortPosition(OpenGLState::SORT_ZFILL);
+        zPass.stage0 = triplet.diffuse;
+        zPass.texture0 = getTextureOrInteractionDefault(triplet.diffuse)->getGLTexNum();
+
+        zPass.glProgram = _renderSystem.getGLProgramFactory().getBuiltInProgram("depthFillAlpha");
+    }
+#endif
     // Add the DBS pass
     OpenGLState& dbsPass = appendDefaultPass();
 
     // Populate the textures and remember the stage reference
     setGLTexturesFromTriplet(dbsPass, triplet);
 
     // Set render flags
-    dbsPass.setRenderFlag(RENDER_BLEND);
+    //dbsPass.setRenderFlag(RENDER_BLEND);
     dbsPass.setRenderFlag(RENDER_FILL);
     dbsPass.setRenderFlag(RENDER_TEXTURE_2D);
     dbsPass.setRenderFlag(RENDER_CULLFACE);

radiantcore/rendersystem/backend/OpenGLShaderPass.cpp

@@ -11,6 +11,8 @@
 #include "debugging/render.h"
 #include "debugging/gl.h"
 
+#include "glprogram/GLSLDepthFillAlphaProgram.h"
+
 namespace render
 {
 
@@ -303,6 +305,20 @@ void OpenGLShaderPass::applyState(OpenGLState& current,
         {
             current.glProgram->enable();
         }
+
+        // Check if we need to set the alpha test value
+        if ((requiredState & (RENDER_ALPHATEST | RENDER_FILL)) == (RENDER_ALPHATEST | RENDER_FILL))
+        {
+            auto zFillAlphaProgram = dynamic_cast<GLSLDepthFillAlphaProgram*>(current.glProgram);
+
+            if (zFillAlphaProgram != nullptr)
+            {
+                zFillAlphaProgram->applyAlphaTest(_glState.alphaThreshold);
+
+                setTextureState(current.texture0, _glState.texture0, GL_TEXTURE0, GL_TEXTURE_2D);
+                setupTextureMatrix(GL_TEXTURE0, _glState.stage0);
+            }
+        }
     }
 
     // State changes. Only perform these if changingBitsMask > 0, since if there are

radiantcore/rendersystem/backend/glprogram/GLSLBumpProgram.h

@@ -9,6 +9,7 @@ namespace render
 class GLSLBumpProgram : 
     public GLSLProgramBase
 {
+private:
 	// The value all lights should be scaled by, obtained from the game description
 	float _lightScale;
 
@@ -20,9 +21,6 @@ class GLSLBumpProgram :
     int _locAmbientLight;
     int _locInvertVCol;
 
-    // Program object identifier
-    GLuint _programObj;
-
 public:
 
     /* GLProgram implementation */

radiantcore/rendersystem/backend/glprogram/GLSLDepthFillAlphaProgram.cpp

@@ -23,6 +23,49 @@ void GLSLDepthFillAlphaProgram::create()
         DEPTHFILL_ALPHA_VP_FILENAME, DEPTHFILL_ALPHA_FP_FILENAME
     );
 
+    glBindAttribLocation(_programObj, ATTR_TEXCOORD, "attr_TexCoord0");
+
+    glLinkProgram(_programObj);
+
+    debug::assertNoGlErrors();
+
+    _locAlphaTest = glGetUniformLocation(_programObj, "u_alpha_test");
+
+    glUseProgram(_programObj);
+    debug::assertNoGlErrors();
+
+    GLint samplerLoc = glGetUniformLocation(_programObj, "u_diffuse");
+    glUniform1i(samplerLoc, 0);
+
+    debug::assertNoGlErrors();
+}
+
+void GLSLDepthFillAlphaProgram::enable()
+{
+    GLSLProgramBase::enable();
+
+    glEnableVertexAttribArrayARB(ATTR_TEXCOORD);
+}
+
+void GLSLDepthFillAlphaProgram::disable()
+{
+    GLSLProgramBase::disable();
+
+    glDisableVertexAttribArrayARB(ATTR_TEXCOORD);
+}
+
+void GLSLDepthFillAlphaProgram::applyAlphaTest(float alphaTest)
+{
+    glUniform1f(_locAlphaTest, alphaTest);
+
+    debug::assertNoGlErrors();
+
+    glActiveTexture(GL_TEXTURE0);
+    glClientActiveTexture(GL_TEXTURE0);
+
+    glMatrixMode(GL_TEXTURE);
+    glLoadIdentity();
+
     debug::assertNoGlErrors();
 }
 

radiantcore/rendersystem/backend/glprogram/GLSLDepthFillAlphaProgram.h

@@ -8,8 +8,15 @@ namespace render
 class GLSLDepthFillAlphaProgram :
     public GLSLProgramBase
 {
+private:
+    GLint _locAlphaTest;
+
 public:
     void create() override;
+    void enable() override;
+    void disable() override;
+
+    void applyAlphaTest(float alphaTest);
 };
 
 }