diff --git a/Effects/landmass.eff b/Effects/landmass.eff
index d7141c06e..1f6114987 100644
--- a/Effects/landmass.eff
+++ b/Effects/landmass.eff
@@ -87,7 +87,7 @@
Shaders/landmass-g.vert
Shaders/landmass.geom
Shaders/landmass.frag
- 20
+ 18
triangles
triangle-strip
diff --git a/Shaders/landmass-g.vert b/Shaders/landmass-g.vert
index fe89ab7a3..afcffa7db 100644
--- a/Shaders/landmass-g.vert
+++ b/Shaders/landmass-g.vert
@@ -1,19 +1,55 @@
+#version 120
+
+// "landmass" effect with forest construction using a geometry
+// shader. The landmass effect includes a bumpmap effect as well as
+// variation by altitude.
+//
+// The fragment shader needs position and normals in model and eye
+// coordinates. This vertex shader calculates the positions and
+// normals of the forest polygons so the geometry shader can do as
+// little as possible.
+
+// Input for the geometry shader. "raw" means terrain model
+// coordinates; that's a tile-local coordinate system, with z as local
+// up. "ec" means eye coordinates.
+
+// model position of original terrain poly; the bottom of the forest.
varying vec4 rawposIn;
+// model forest top
+varying vec4 rawTopIn;
+// model normal
varying vec3 NormalIn;
+varying vec4 ecPosIn;
+varying vec4 ecTopIn;
+varying vec3 ecNormalIn;
+// eye spacce tangent and binormal
varying vec3 VTangentIn;
varying vec3 VBinormalIn;
+// screen-space position of top
+varying vec4 positionTopIn;
+// constant color component
+varying vec4 constantColorIn;
attribute vec3 tangent;
attribute vec3 binormal;
+uniform float canopy_height;
+
void main(void)
{
- rawposIn = gl_Vertex;
+ rawposIn = gl_Vertex;
+ ecPosIn = gl_ModelViewMatrix * gl_Vertex;
NormalIn = normalize(gl_Normal);
+ rawTopIn = rawposIn + vec4(0.0, 0.0, canopy_height, 0.0);
+ ecTopIn = gl_ModelViewMatrix * rawTopIn;
+ ecNormalIn = gl_NormalMatrix * NormalIn;
VTangentIn = gl_NormalMatrix * tangent;
VBinormalIn = gl_NormalMatrix * binormal;
gl_FrontColor = gl_Color;
gl_Position = ftransform();
+ positionTopIn = gl_ModelViewProjectionMatrix * rawTopIn;
gl_TexCoord[0] = gl_TextureMatrix[0] * gl_MultiTexCoord0;
+ constantColorIn = gl_FrontMaterial.emission
+ + gl_Color * (gl_LightModel.ambient + gl_LightSource[0].ambient);
}
diff --git a/Shaders/landmass.geom b/Shaders/landmass.geom
index 01bc9f095..5dc4a8bd4 100644
--- a/Shaders/landmass.geom
+++ b/Shaders/landmass.geom
@@ -1,82 +1,116 @@
#version 120
#extension GL_EXT_geometry_shader4 : enable
+// Geometry shader that creates a prism from a terrain triangle,
+// resulting in a forest effect.
+//
+// A geometry shader should do as little computation as possible.
+
+// See landmass-g.vert for a description of the inputs.
varying in vec4 rawposIn[];
varying in vec3 NormalIn[];
+varying in vec4 rawTopIn[];
+varying in vec4 ecPosIn[];
+varying in vec4 ecTopIn[];
+varying in vec3 ecNormalIn[];
varying in vec3 VTangentIn[];
varying in vec3 VBinormalIn[];
+varying in vec4 positionTopIn[];
+varying in vec4 constantColorIn[];
+uniform float canopy_height;
+
+// model position
varying out vec4 rawpos;
+// eye position
varying out vec4 ecPosition;
+// eye space surface matrix
varying out vec3 VNormal;
varying out vec3 VTangent;
varying out vec3 VBinormal;
+// model normal
varying out vec3 Normal;
varying out vec4 constantColor;
varying out float bump;
-uniform float canopy_height;
-
-void createVertex(int i, int j, float offset, float s)
+// Emit one vertex of the forest geometry.
+// parameters:
+// i - index into original terrain triangle
+void doVertex(in int i, in vec4 pos, in vec4 ecpos, in vec4 screenpos,
+ in vec3 rawNormal, in vec3 normal, in float s)
{
- rawpos = rawposIn[i] + offset * vec4(NormalIn[i], 0.0);
- ecPosition = gl_ModelViewMatrix * rawpos;
- if ( s == 0.0 )
- {
- vec4 v;
- if (j < i)
- {
- v = rawposIn[j] - rawposIn[i];
- Normal = normalize(cross( NormalIn[i], v.xyz ));
- }
- else
- {
- v = rawposIn[i] - rawposIn[j];
- Normal = normalize(cross( NormalIn[j], v.xyz ));
- }
- }
- else
- {
- Normal = NormalIn[i];
- }
- VNormal = normalize(gl_NormalMatrix * Normal);
- VTangent = VTangentIn[i];
+ rawpos = pos;
+ ecPosition = ecpos;
+ Normal = rawNormal;
+ VNormal = normal;
+ VTangent = VTangentIn[i];
VBinormal = VBinormalIn[i];
bump = s;
gl_FrontColor = gl_FrontColorIn[i];
- constantColor = gl_FrontMaterial.emission
- + gl_FrontColorIn[i] * (gl_LightModel.ambient + gl_LightSource[0].ambient);
- gl_Position = gl_ProjectionMatrix * ecPosition;
+ constantColor = constantColorIn[i];
+ gl_Position = screenpos;
gl_TexCoord[0] = gl_TexCoordIn[i][0];
EmitVertex();
}
+vec3 rawSideNormal[3];
+vec3 sideNormal[3];
+
+// Emit a vertex for a forest side triangle
+void doSideVertex(in int vertIdx, in int sideIdx, vec4 pos, in vec4 ecpos,
+ in vec4 screenpos)
+{
+ doVertex(vertIdx, pos, ecpos, screenpos, rawSideNormal[sideIdx],
+ sideNormal[sideIdx], 0.0);
+}
+
void main(void)
{
- if (canopy_height > 0.01) {
- createVertex(0, 1, canopy_height, 0.0);
- createVertex(0, 1, 0.0, 0.0);
- createVertex(1, 0, canopy_height, 0.0);
- createVertex(1, 0, 0.0, 0.0);
- EndPrimitive();
- createVertex(1, 2, canopy_height, 0.0);
- createVertex(1, 2, 0.0, 0.0);
- createVertex(2, 1, canopy_height, 0.0);
- createVertex(2, 1, 0.0, 0.0);
- EndPrimitive();
- createVertex(2, 0, canopy_height, 0.0);
- createVertex(2, 0, 0.0, 0.0);
- createVertex(0, 2, canopy_height, 0.0);
- createVertex(0, 2, 0.0, 0.0);
- EndPrimitive();
- createVertex(0, 1, 0.0, 0.0);
- createVertex(1, 2, 0.0, 0.0);
- createVertex(2, 0, 0.0, 0.0);
- EndPrimitive();
- }
- createVertex(0, 1, canopy_height, 1.0);
- createVertex(1, 2, canopy_height, 1.0);
- createVertex(2, 0, canopy_height, 1.0);
- EndPrimitive();
+ rawSideNormal[0] = normalize(cross((rawposIn[1] - rawposIn[0]).xyz,
+ NormalIn[0]));
+ rawSideNormal[1] = normalize(cross((rawposIn[2] - rawposIn[1]).xyz,
+ NormalIn[1]));
+ rawSideNormal[2] = normalize(cross((rawposIn[0] - rawposIn[2]).xyz,
+ NormalIn[2]));
+ for (int i = 0; i < 3; ++i)
+ sideNormal[i] = gl_NormalMatrix * rawSideNormal[i];
+ if (canopy_height > 0.01) {
+ // Sides
+ doSideVertex(0, 0, rawTopIn[0], ecTopIn[0], positionTopIn[0]);
+ doSideVertex(0, 0, rawposIn[0], ecPosIn[0], gl_PositionIn[0]);
+ doSideVertex(1, 0, rawTopIn[1], ecTopIn[1], positionTopIn[1]);
+ doSideVertex(1, 0, rawposIn[1], ecPosIn[1], gl_PositionIn[1]);
+
+ doSideVertex(2, 1, rawTopIn[2], ecTopIn[2], positionTopIn[2]);
+ doSideVertex(2, 1, rawposIn[2], ecPosIn[2], gl_PositionIn[2]);
+
+ doSideVertex(0, 2, rawTopIn[0], ecTopIn[0], positionTopIn[0]);
+ doSideVertex(0, 2, rawposIn[0], ecPosIn[0], gl_PositionIn[0]);
+ // Degenerate triangles; avoids EndPrimitive()
+ doSideVertex(0, 2, rawposIn[0], ecPosIn[0], gl_PositionIn[0]);
+ doVertex(0, rawTopIn[0], ecTopIn[0], positionTopIn[0], NormalIn[0],
+ ecNormalIn[0], 1.0);
+ // Top
+ }
+ doVertex(0, rawTopIn[0], ecTopIn[0], positionTopIn[0], NormalIn[0],
+ ecNormalIn[0], 1.0);
+ doVertex(1, rawTopIn[1], ecTopIn[1], positionTopIn[1], NormalIn[1],
+ ecNormalIn[1], 1.0);
+ doVertex(2, rawTopIn[2], ecTopIn[2], positionTopIn[2], NormalIn[2],
+ ecNormalIn[2], 1.0);
+ // Don't render "bottom" triangle for now; it's hidden.
+#if 0
+ // degenerate
+ doVertex(2, rawTopIn[2], ecTopIn[2], positionTopIn[2], NormalIn[2],
+ ecNormalIn[2], 1.0);
+ // bottom
+ doVertex(0, rawposIn[0], ecPosIn[0], gl_PositionIn[0], NormalIn[0],
+ ecNormalIn[0], 1.0);
+ doVertex(1, rawposIn[1], ecPosIn[1], gl_PositionIn[1], NormalIn[1],
+ ecNormalIn[1], 1.0);
+ doVertex(2, rawposIn[2], ecPosIn[2], gl_PositionIn[2], NormalIn[2],
+ ecNormalIn[2], 1.0);
+#endif
+ EndPrimitive();
}