From 1a1d603c7618bc201d64c7f2342e3e241f5a10d9 Mon Sep 17 00:00:00 2001
From: hodasemi <michaelh.95@t-online.de>
Date: Thu, 6 Dec 2018 11:22:55 +0100
Subject: [PATCH] finite differences test

---
 exercise2/glsl/terrain.vert | 16 ++++++++++++++++
 exercise2/src/Viewer.cpp    | 13 +++++++++++--
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/exercise2/glsl/terrain.vert b/exercise2/glsl/terrain.vert
index 2db7089..1e4a7f0 100644
--- a/exercise2/glsl/terrain.vert
+++ b/exercise2/glsl/terrain.vert
@@ -31,6 +31,22 @@ void main()
 {
 	vec2 instanced_pos = vec2(position.x + offset.x, position.z + offset.y);
 	vec4 terrain_position = vec4(instanced_pos.x, getTerrainHeight(instanced_pos), instanced_pos.y, position.w);
+
+	/*
+	// read neightbor heights using an arbitrary small offset
+	vec3 off = vec3(1.0, 1.0, 0.0);
+	float hL = getTerrainHeight(position.xz - off.xz);
+	float hR = getTerrainHeight(position.xz + off.xz);
+	float hD = getTerrainHeight(position.xz - off.zy);
+	float hU = getTerrainHeight(position.xz + off.zy);
+
+	// deduce terrain normal
+	n.x = hL - hR;
+	n.y = hD - hU;
+	n.z = 2.0;
+	n = normalize(n);
+	*/
+
 	n = calculate_normal(terrain_position);
 	//n = vec3(0.0, 1.0, 0.0);
 
diff --git a/exercise2/src/Viewer.cpp b/exercise2/src/Viewer.cpp
index 00b6823..2347429 100644
--- a/exercise2/src/Viewer.cpp
+++ b/exercise2/src/Viewer.cpp
@@ -53,7 +53,7 @@ Viewer::Viewer()
 	for (int j = -max_offset; j < max_offset; j++)
 		for (int i = -max_offset; i < max_offset; i++)
 		{
-			offsets.emplace_back((float)(i * PATCH_SIZE), (float)(j * PATCH_SIZE));
+			offsets.emplace_back((float)(i * (int32_t)PATCH_SIZE), (float)(j * (int32_t)PATCH_SIZE));
 		}
 }
 
@@ -352,9 +352,18 @@ void Viewer::drawContents()
 	glEnable(GL_DEPTH_TEST);
 	terrainVAO.bind();
 
+	/*
+	for (auto &i : instances)
+	{
+		std::cout << i.x() << " " << i.y() << std::endl;
+	}
+
+	abort();
+	*/
+
 	offsetBuffer.bind();
 	offsetBuffer.uploadData(instances);
-	glVertexAttribDivisor(offset_buffer_location, instances.size());
+	glVertexAttribDivisor(offset_buffer_location, 1);
 
 	terrainShader.bind();