From c3c2265ddd3e89ae3f66596f82c553b4fc085bd2 Mon Sep 17 00:00:00 2001
From: Andrzej Kapolka <drzej.k@gmail.com>
Date: Wed, 30 Jul 2014 18:14:11 -0700
Subject: [PATCH] Hide the unset (black) bits.

---
 .../resources/shaders/metavoxel_heightfield.vert  | 10 +++++-----
 interface/src/MetavoxelSystem.cpp                 | 15 +++++++++++++--
 libraries/metavoxels/src/AttributeRegistry.cpp    |  3 ++-
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/interface/resources/shaders/metavoxel_heightfield.vert b/interface/resources/shaders/metavoxel_heightfield.vert
index a5e7ec66c1..3cf43e87cd 100644
--- a/interface/resources/shaders/metavoxel_heightfield.vert
+++ b/interface/resources/shaders/metavoxel_heightfield.vert
@@ -21,13 +21,13 @@ void main(void) {
     // transform and store the normal for interpolation
     normal = normalize(gl_ModelViewMatrix * vec4(0.0, 1.0, 0.0, 0.0));
     
-    // pass along the vertex color
-    gl_FrontColor = gl_Color;
-    
     // pass along the texture coordinates
     gl_TexCoord[0] = gl_MultiTexCoord0;
     
     // add the height to the position
-    gl_Position = gl_ModelViewProjectionMatrix * (gl_Vertex +
-        vec4(0.0, texture2D(heightMap, gl_MultiTexCoord0.st).r, 0.0, 0.0));
+    float height = texture2D(heightMap, gl_MultiTexCoord0.st).r;
+    gl_Position = gl_ModelViewProjectionMatrix * (gl_Vertex + vec4(0.0, height, 0.0, 0.0));
+    
+    // the zero height should be invisible
+    gl_FrontColor = vec4(1.0, 1.0, 1.0, step(height, 0.0));
 }
diff --git a/interface/src/MetavoxelSystem.cpp b/interface/src/MetavoxelSystem.cpp
index d357ab5ce4..16ce98c65c 100644
--- a/interface/src/MetavoxelSystem.cpp
+++ b/interface/src/MetavoxelSystem.cpp
@@ -397,7 +397,11 @@ void HeightfieldBuffer::render() {
 QHash<int, HeightfieldBuffer::BufferPair> HeightfieldBuffer::_bufferPairs;
 
 void HeightfieldPreview::render(const glm::vec3& translation, float scale) const {
-    glColor4f(1.0f, 1.0f, 1.0f, 0.75f);
+    glDisable(GL_BLEND);
+    glEnable(GL_ALPHA_TEST);
+    glAlphaFunc(GL_EQUAL, 0.0f);
+    
+    glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
     
     glEnableClientState(GL_VERTEX_ARRAY);
     glEnableClientState(GL_TEXTURE_COORD_ARRAY);
@@ -418,6 +422,9 @@ void HeightfieldPreview::render(const glm::vec3& translation, float scale) const
     
     glDisableClientState(GL_TEXTURE_COORD_ARRAY);
     glDisableClientState(GL_VERTEX_ARRAY);
+    
+    glDisable(GL_ALPHA_TEST);
+    glEnable(GL_BLEND);
 }
 
 BufferDataAttribute::BufferDataAttribute(const QString& name) :
@@ -695,7 +702,10 @@ void DefaultMetavoxelRendererImplementation::render(MetavoxelData& data, Metavox
     
     _pointProgram.release();
     
-    glColor4f(1.0f, 1.0f, 1.0f, 0.0f);
+    glEnable(GL_ALPHA_TEST);
+    glAlphaFunc(GL_EQUAL, 0.0f);
+    
+    glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
     
     _heightfieldProgram.bind();
     
@@ -710,6 +720,7 @@ void DefaultMetavoxelRendererImplementation::render(MetavoxelData& data, Metavox
     glDisableClientState(GL_TEXTURE_COORD_ARRAY);
     glDisableClientState(GL_VERTEX_ARRAY);
     
+    glDisable(GL_ALPHA_TEST);
     glEnable(GL_BLEND);
 }
 
diff --git a/libraries/metavoxels/src/AttributeRegistry.cpp b/libraries/metavoxels/src/AttributeRegistry.cpp
index 499f8146cf..7219e9da41 100644
--- a/libraries/metavoxels/src/AttributeRegistry.cpp
+++ b/libraries/metavoxels/src/AttributeRegistry.cpp
@@ -578,7 +578,8 @@ bool HeightfieldAttribute::merge(void*& parent, void* children[], bool postRead)
         int childSizePlusOne = childSize + 1;
         for (int z = 0; z < halfSize; z++) {
             for (char* end = dest + halfSize; dest != end; src += 2) {
-                *dest++ = yOffset + (qMax(qMax(src[0], src[1]), qMax(src[childSize], src[childSizePlusOne])) >> 1);
+                int max = qMax(qMax(src[0], src[1]), qMax(src[childSize], src[childSizePlusOne]));
+                *dest++ = (max == 0) ? 0 : (yOffset + (max >> 1));
             }
             dest += halfSize;
             src += childSize;