Implemented DX clipping rules to match CG version. Uses dx_clipping varying.

Review URL: http://codereview.chromium.org/1646016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@45069 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 53 insertions, 6 deletions

diff --git a/o3d/cg_to_glsl/convert.py b/o3d/cg_to_glsl/convert.py
index 8eb86ec..3efb3ea 100755
--- a/o3d/cg_to_glsl/convert.py
+++ b/o3d/cg_to_glsl/convert.py
@@ -18,7 +18,7 @@ import sys
 #
 # * changes 'uniform vecN var[N]' to 'uniform matN var';
 #
-# * renames gl_Vertex and gl_MultiTexCoordN to position and texcoordsN
+# * renames gl_Vertex and gl_MultiTexCoordN to position and texcoordN
 #   respectively and adds attribute declarations;
 #
 # * prints the results to standard output, separating them with SplitMarker
@@ -77,14 +77,32 @@ def fix_glsl_body(body, input_mapping):
 
   for n in xrange(8):
     if 'gl_MultiTexCoord%d' % n in body:
-      # Change gl_MultiTexCoordN (0<=N<=7) to texcoordsN and add attribute
+      # Change gl_MultiTexCoordN (0<=N<=7) to texcoordN and add attribute
       # declaration.
-      body = re.sub(r'\bgl_MultiTexCoord%d\b' % n, 'texcoords%d' % n, body)
-      attributes.append('attribute vec4 texcoords%d;' % n)
+      body = re.sub(r'\bgl_MultiTexCoord%d\b' % n, 'texcoord%d' % n, body)
+      attributes.append('attribute vec4 texcoord%d;' % n)
 
   # ATTRIBUTES_TO_SEMANTICS should have taken care of normals.
   assert 'gl_Normal' not in body
 
+  if 'gl_Position' in body:
+    # If there is exactly one assignment to gl_Position, modify it similar to
+    # how RewriteVertexProgramSource in gl/effect_gl.cc does it.  The input is
+    # taken from vec4 dx_clipping uniform.
+    #
+    # If there is more than one gl_Position mentioned in the shader, the
+    # converter fails.
+    assert len(re.findall('gl_Position', body)) == 1
+    attributes.append('vec4 _glPositionTemp;')
+    attributes.append('uniform vec4 dx_clipping;')
+    body = re.sub(r'\bgl_Position\b([^;]*);',
+                  r'_glPositionTemp\1; gl_Position = vec4(' +
+                  r'_glPositionTemp.x + _glPositionTemp.w * dx_clipping.x, ' +
+                  r'dx_clipping.w * ' +
+                  r'(_glPositionTemp.y + _glPositionTemp.w * dx_clipping.y), ' +
+                  r'_glPositionTemp.z * 2 - _glPositionTemp.w, ' +
+                  r'_glPositionTemp.w);', body)
+
   return '\n'.join(attributes) + '\n\n' + body
 
 
diff --git a/o3d/core/cross/gles2/effect_gles2.cc b/o3d/core/cross/gles2/effect_gles2.cc
index 060f46b..88157b0 100644
--- a/o3d/core/cross/gles2/effect_gles2.cc
+++ b/o3d/core/cross/gles2/effect_gles2.cc
@@ -404,6 +404,8 @@ void EffectGLES2::UpdateShaderUniformsFromEffect(
     GLES2Parameter gl_param = i->first;
     i->second->SetEffectParam(renderer_, gl_param);
   }
+  renderer_->UpdateDxClippingUniform(
+      glGetUniformLocation(gl_program_, "dx_clipping"));
   CHECK_GL_ERROR();
 }
 
diff --git a/o3d/core/cross/gles2/param_cache_gles2.cc b/o3d/core/cross/gles2/param_cache_gles2.cc
index 5a6fc85..4dc4d50 100644
--- a/o3d/core/cross/gles2/param_cache_gles2.cc
+++ b/o3d/core/cross/gles2/param_cache_gles2.cc
@@ -601,7 +601,8 @@ static void ScanVaryingParameters(GLuint gl_program,
         gl_program, ii, max_len + 1, &length, &size, &type, name_buffer.get());
     // TODO(gman): Should we check for error?
     GLint location = glGetAttribLocation(gl_program, name_buffer.get());
-    param_cache_gl->varying_map().insert(std::make_pair(location, ii));
+    if (location != -1)
+      param_cache_gl->varying_map().insert(std::make_pair(location, ii));
   }
 }
 
diff --git a/o3d/core/cross/gles2/renderer_gles2.cc b/o3d/core/cross/gles2/renderer_gles2.cc
index e6012f4..71d5c72 100644
--- a/o3d/core/cross/gles2/renderer_gles2.cc
+++ b/o3d/core/cross/gles2/renderer_gles2.cc
@@ -1343,7 +1343,27 @@ void RendererGLES2::UpdateHelperConstant(float width, float height) {
   // If render-targets are active, pass -1 to invert the Y axis.  OpenGLES2 uses
   // a different viewport orientation than DX.  Without the inversion, the
   // output of render-target rendering will be upside down.
-  // TODO(piman): actually implement this.
+  CHECK_GL_ERROR();
+
+  if (RenderSurfaceActive()) {
+    dx_clipping_[0] = 1.f / width;
+    dx_clipping_[1] = -1.f / height;
+    dx_clipping_[2] = 2.f;
+    dx_clipping_[3] = -1.f;
+  } else {
+    dx_clipping_[0] = (1.0f + 2.0f * (-dest_x_offset())) / width;
+    dx_clipping_[1] = (-1.0f + 2.0f * dest_y_offset()) / height;
+    dx_clipping_[2] = 2.0f;
+    dx_clipping_[3] = 1.0f;
+  }
+}
+
+// Programs the helper constants into the hardware.
+void RendererGLES2::UpdateDxClippingUniform(GLint location) {
+  // For some reason, if location is -1 an error is signalled, despite the spec
+  // saying it is OK.
+  if (location != -1)
+    glUniform4fv(location, 1, dx_clipping_);
   CHECK_GL_ERROR();
 }
 
diff --git a/o3d/core/cross/gles2/renderer_gles2.h b/o3d/core/cross/gles2/renderer_gles2.h
index 289101c..6036c73 100644
--- a/o3d/core/cross/gles2/renderer_gles2.h
+++ b/o3d/core/cross/gles2/renderer_gles2.h
@@ -179,6 +179,9 @@ class RendererGLES2 : public Renderer {
     return next_texture_unit_++;
   }
 
+  // Programs the helper constants into the hardware.
+  void UpdateDxClippingUniform(GLint location);
+
  protected:
   // Keep the constructor protected so only factory methods can create
   // renderers.
@@ -354,6 +357,9 @@ class RendererGLES2 : public Renderer {
   // The next texture unit to use. This is reset with ResetTextureUnit
   // and retrieved with GetNextTextureUnit.
   GLenum next_texture_unit_;
+
+  // Transform matrix coefficients to match DX clipping rules.
+  GLfloat dx_clipping_[4];
 };
 
 }  // namespace o3d