From: Mikko Rasa <tdb@tdb.fi>
Date: Wed, 25 Nov 2015 11:53:24 +0000 (+0200)
Subject: Add geometry builder for sphere
X-Git-Url: http://git.tdb.fi/?p=libs%2Fgl.git;a=commitdiff_plain;h=093ed86110ebbcd1bc09f693a89bac09ec8198e4

Add geometry builder for sphere
---

diff --git a/source/sphere.cpp b/source/sphere.cpp
new file mode 100644
index 00000000..0bedf150
--- /dev/null
+++ b/source/sphere.cpp
@@ -0,0 +1,81 @@
+#include <cmath>
+#include "primitivebuilder.h"
+#include "sphere.h"
+
+namespace Msp {
+namespace GL {
+
+UvSphereBuilder::UvSphereBuilder(float r, unsigned s, unsigned n):
+	radius(r),
+	segments(s),
+	rings(n)
+{
+	if(segments<3)
+		segments = 3;
+
+	if(rings==0)
+		rings = (segments+1)/2;
+	else if(rings<2)
+		rings = 2;
+}
+
+void UvSphereBuilder::build(PrimitiveBuilder &builder) const
+{
+	float u_scale = 1.0f/segments;
+	float v_scale = 1.0f/rings;
+	adjust_texture_scale(u_scale, v_scale, radius*M_PI*2, radius*M_PI);
+
+	for(unsigned i=0; i<=rings; ++i)
+	{
+		float av = i*M_PI/rings-M_PI/2;
+		float cv = cos(av);
+		float sv = sin(av);
+
+		for(unsigned j=0; j<=segments; ++j)
+		{
+			float au = j*M_PI*2/segments;
+			float cu = cos(au);
+			float su = sin(au);
+
+			builder.normal(cv*cu, cv*su, sv);
+			builder.texcoord(j*u_scale, i*v_scale);
+			if(generate_tbn)
+			{
+				builder.tangent(-su, cu, 0);
+				builder.binormal(-sv*cu, -sv*su, cv);
+			}
+			builder.vertex(cv*cu*radius, cv*su*radius, sv*radius);
+		}
+	}
+
+	builder.begin(TRIANGLES);
+	for(unsigned j=0; j<segments; ++j)
+	{
+		builder.element(j);
+		builder.element(segments+2+j);
+		builder.element(segments+1+j);
+	}
+	unsigned top = (rings+1)*(segments+1)-1;
+	for(unsigned j=0; j<segments; ++j)
+	{
+		builder.element(top-j);
+		builder.element(top-(segments+2+j));
+		builder.element(top-(segments+1+j));
+	}
+	builder.end();
+
+	for(unsigned i=1; i<rings; ++i)
+	{
+		builder.begin(TRIANGLE_STRIP);
+		unsigned base = i*(segments+1);
+		for(unsigned j=0; j<=segments; ++j)
+		{
+			builder.element(base+segments+1+j);
+			builder.element(base+j);
+		}
+		builder.end();
+	}
+}
+
+} // namespace GL
+} // namespace Msp
diff --git a/source/sphere.h b/source/sphere.h
new file mode 100644
index 00000000..b69c4083
--- /dev/null
+++ b/source/sphere.h
@@ -0,0 +1,26 @@
+#ifndef MSP_GL_SPHERE_H_
+#define MSP_GL_SPHERE_H_
+
+#include "geometrybuilder.h"
+
+namespace Msp {
+namespace GL {
+
+class UvSphereBuilder: public GeometryBuilder
+{
+private:
+	float radius;
+	unsigned segments;
+	unsigned rings;
+
+public:
+	UvSphereBuilder(float, unsigned, unsigned = 0);
+
+	using GeometryBuilder::build;
+	virtual void build(PrimitiveBuilder &) const;
+};
+
+} // namespace GL
+} // namespace Msp
+
+#endif