X-Git-Url: http://git.mutantstargoat.com?p=demo;a=blobdiff_plain;f=src%2Fmeshgen.cc;h=ff7906d4a251803ebecdac612452ec3d6f1fcadc;hp=fb4fae2545a797c338f4c2bdd3e2d9060b512548;hb=197f20b5d4db937029f7b585be23ee7fe5da66dc;hpb=dd0aabd3aed66f9c5d25a9e8bcbbb07c7f886085

diff --git a/src/meshgen.cc b/src/meshgen.cc
index fb4fae2..ff7906d 100644
--- a/src/meshgen.cc
+++ b/src/meshgen.cc
@@ -120,4 +120,99 @@ void gen_geosphere(Mesh *mesh, float rad, int subdiv, bool hemi)
 		mesh->indices[i] = i;
 	}
 	mesh->update_vertex_data();
-}
\ No newline at end of file
+}
+
+// ------ heightfield ------
+
+static Vec3 hfield_vertex(float u, float v, float h, float xsz,
+		float ysz, float height)
+{
+	float x = u * xsz - xsz / 2.0;
+	float y = h * height;
+	float z = v * ysz - ysz / 2.0;
+
+	return Vec3(x, y, z);
+}
+
+void gen_heightfield(Mesh *mesh, float xsz, float ysz, float height, int usub,
+		int vsub, float (*calc_height)(float u, float v, void *ptr), void *ptr)
+{
+	/* 
+	usub and vsub is the number of subdivision at each axis
+	(heightfield = grid) 
+	*/
+	if(usub < 1)
+		usub = 1;
+
+	if(vsub < 1)
+		vsub = 1;
+
+	int num_uvertices = usub + 1;
+	int num_vvertices = vsub + 1;
+
+	int num_quads = usub * vsub;
+	int num_triangles = num_quads * 2;
+
+	int num_vertices = num_uvertices * num_vvertices;
+
+	mesh->vertices.resize(num_vertices);
+	mesh->normals.resize(num_vertices);
+	mesh->tex_coords.resize(num_vertices);
+	mesh->indices.resize(num_triangles * 3);
+
+	int vidx = 0;
+	float du = 1.0 / (float)num_uvertices;
+	float dv = 1.0 / (float)num_vvertices;
+
+	for(int i=0; i<num_vvertices; i++) {
+		float v = (float)i / (float)num_vvertices;
+		for(int j=0; j<num_uvertices; j++) {
+			float u = (float)j / (float)num_uvertices;
+			Vec3 vtx = hfield_vertex(u, v, calc_height(u, v, ptr), xsz, ysz, height);
+
+			/* calculating normal with forward differences:
+			slopes in x, z, axis */
+
+			Vec3 tangent = hfield_vertex(u + du, v, calc_height(u + du, v, ptr),
+					xsz, ysz, height) - vtx;
+
+			Vec3 bitangent = hfield_vertex(u, v + dv, calc_height(u, v + dv, ptr),
+					xsz, ysz, height) - vtx;
+
+			Vec3 normal = normalize(cross(tangent, bitangent));
+
+			mesh->vertices[vidx] = vtx;
+			mesh->normals[vidx] = normal;
+			mesh->tex_coords[vidx] = Vec2(u, v);
+
+			vidx++;
+		}
+	}
+
+	/*
+		indices: 
+	*/
+	uint16_t *iptr = &mesh->indices[0];
+
+	for(int i=0; i<vsub; i++) {
+		for(int j=0; j<usub; j++) {
+			int a = num_vvertices * i + j;
+			int b = a + 1;
+			int d = num_vvertices * (i + 1) + j;
+			int c = d + 1;
+
+			/* 1st triangle */
+
+			*iptr++ = a;
+			*iptr++ = b;
+			*iptr++ = c;
+
+			/* 2nd triangle */
+
+			*iptr++ = c;
+			*iptr++ = d;
+			*iptr++ = a;
+		}
+	}
+	mesh->update_vertex_data();
+}