rework Strand to use VBOs

Aquaria/Segmented.h

@@ -22,6 +22,7 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 #define SEGMENTED_H
 
 #include "../BBGE/Quad.h"
+#include "VertexBuffer.h"
 
 class Segmented
 {
@@ -51,6 +52,8 @@ public:
 protected:
 	void onUpdate(float dt) OVERRIDE;
 	void onRender(const RenderState& rs) const OVERRIDE;
+
+	DynamicGPUBuffer gpubuf;
 };
 
 #endif

Aquaria/Strand.cpp

@@ -21,12 +21,16 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 #include "Segmented.h"
 #include "RenderBase.h"
 
-Strand::Strand(const Vector &position, size_t segs, size_t dist) : RenderObject(), Segmented(dist, dist)
+Strand::Strand(const Vector &position, size_t segs, size_t dist)
+	: RenderObject(), Segmented(dist, dist)
+	, gpubuf(GPUBUF_DYNAMIC | GPUBUF_VERTEXBUF)
 {
+	assert(segs);
 	cull = false;
 	segments.resize(segs);
 	for (size_t i = 0; i < segments.size(); i++)
 	{
+		// FIXME: This is super costly to waste an entire RenderObject just to store a position.
 		segments[i] = new RenderObject;
 	}
 	initSegments(position);
@@ -47,46 +51,69 @@ void Strand::onUpdate(float dt)
 {
 	RenderObject::onUpdate(dt);
 	updateSegments(position);
+
+	const size_t numSegments = segments.size();
+
+	do
+	{
+		const size_t bytes = (numSegments+1) * 6 * sizeof(float);
+		float *p = (float*)gpubuf.beginWrite(GPUBUFTYPE_VEC2_RGBA, bytes, GPUACCESS_DEFAULT);
+
+		// Note: We're rewriting all of the vertex data here.
+		// Ideally we'd only rewrite position data since vertex colors never change,
+		// but currently this is to keep buffer layouts simple.
+
+		const float factor = 1.0f / 50.0f;
+		const size_t colorLimit = numSegments<50 ? numSegments : 50;
+		const Vector falloff = color * factor;
+		const float falloffAlpha = 1.0f / float(numSegments);
+		float a = 1.0f;
+		Vector c = color;
+
+		// initial vertex (this is the +1)
+		*p++ = position.x;
+		*p++ = position.y;
+
+		*p++ = c.x;
+		*p++ = c.y;
+		*p++ = c.z;
+		*p++ = a;
+
+		size_t i;
+		for(i = 0; i < colorLimit; ++i)
+		{
+			*p++ = segments[i]->position.x;
+			*p++ = segments[i]->position.y;
+
+			*p++ = c.x;
+			*p++ = c.y;
+			*p++ = c.z;
+			*p++ = a;
+
+			c -= falloff;
+			a -= falloffAlpha;
+		}
+		for( ; i < numSegments; ++i)
+		{
+			*p++ = segments[i]->position.x;
+			*p++ = segments[i]->position.y;
+
+			*p++ = 0.0f;
+			*p++ = 0.0f;
+			*p++ = 0.0f;
+			*p++ = a;
+
+			a -= falloffAlpha;
+		}
+	}
+	while(!gpubuf.commitWrite());
 }
 
 void Strand::onRender(const RenderState& rs) const
 {
-	const size_t numSegments = segments.size();
-	if (numSegments == 0) return;
-
 	glTranslatef(-position.x, -position.y, 0);
 	glLineWidth(1);
 
-	glBegin(GL_LINE_STRIP);
-
-
-	unsigned int r = (unsigned int)(color.x * (255<<8));
-	unsigned int g = (unsigned int)(color.y * (255<<8));
-	unsigned int b = (unsigned int)(color.z * (255<<8));
-	unsigned int a = (255<<8);
-	unsigned int dr = r/50;
-	unsigned int dg = g/50;
-	unsigned int db = b/50;
-	unsigned int da = a/numSegments;
-	glColor4ub(r>>8, g>>8, b>>8, a>>8);
-	glVertex2f(position.x, position.y);
-	glVertex2f(segments[0]->position.x, segments[0]->position.y);
-	const size_t colorLimit = numSegments<50 ? numSegments : 50;
-	size_t i;
-	for (i = 1; i < colorLimit; i++)
-	{
-		r -= dr;
-		g -= dg;
-		b -= db;
-		a -= da;
-		glColor4ub(r>>8, g>>8, b>>8, a>>8);
-		glVertex2f(segments[i]->position.x, segments[i]->position.y);
-	}
-	for (; i < numSegments; i++)
-	{
-		a -= da;
-		glColor4ub(0, 0, 0, a>>8);
-		glVertex2f(segments[i]->position.x, segments[i]->position.y);
-	}
-	glEnd();
+	gpubuf.apply();
+	glDrawArrays(GL_LINE_STRIP, 0, GLsizei(segments.size() + 1));
 }

BBGE/VertexBuffer.cpp

@@ -13,7 +13,8 @@ static unsigned s_lastState = 0; // StateBits
 
 enum StateBits
 {
-    SB_COLOR_FROM_BUFFER = 0x01
+    SB_TC_FROM_BUFFER = 0x01,
+    SB_COLOR_FROM_BUFFER = 0x02
 };
 
 static unsigned toGlUsage(unsigned usage)
@@ -115,6 +116,14 @@ bool DynamicGPUBuffer::commitWrite(size_t used)
     return _commitWrite(used);
 }
 
+bool DynamicGPUBuffer::commitWriteExact(const void * p)
+{
+    const void *origin = _d_map ? _d_map : _h_data;
+    ptrdiff_t d = (const char*)p - (const char*)origin;
+    assert(d == _size);
+    return commitWrite();
+}
+
 bool DynamicGPUBuffer::_commitWrite(size_t used)
 {
     if(_HasARB)
@@ -210,12 +219,15 @@ void DynamicGPUBuffer::apply(BufDataType usetype) const
     const unsigned tcoffset = (u >> 16u) & 0xff;
     const unsigned coloroffset = u >> 24u;
 
-    // vertex and texcoords are always enabled
+    // vertices are always enabled
     glVertexPointer(scalars, gltype, stride, p);
-    if(tcoffset)
-        glTexCoordPointer(2, gltype, stride, (void*)((uintptr_t)p + tcoffset));
 
     unsigned wantedstate = 0;
+    if(tcoffset)
+    {
+        wantedstate |= SB_TC_FROM_BUFFER;
+        glTexCoordPointer(2, gltype, stride, (void*)((uintptr_t)p + tcoffset));
+    }
     if(coloroffset)
     {
         wantedstate |= SB_COLOR_FROM_BUFFER;
@@ -225,6 +237,13 @@ void DynamicGPUBuffer::apply(BufDataType usetype) const
     unsigned wrongbits = wantedstate ^ s_lastState;
     if(wrongbits)
     {
+        if(wrongbits & SB_TC_FROM_BUFFER)
+        {
+            if(wantedstate & SB_TC_FROM_BUFFER)
+                glEnableClientState(GL_TEXTURE_COORD_ARRAY);
+            else
+                glDisableClientState(GL_TEXTURE_COORD_ARRAY);
+        }
         if(wrongbits & SB_COLOR_FROM_BUFFER)
         {
             if(wantedstate & SB_COLOR_FROM_BUFFER)

BBGE/VertexBuffer.h

@@ -27,9 +27,9 @@ enum BufDataType
                                   ^^-- offset of colors, if present */
     GPUBUFTYPE_U16            = 0x00000010,  // densely packed u16, for indexing
     GPUBUFTYPE_VEC2_TC        = 0x00081021,  // xyuv xyuv xyuv
-    GPUBUFTYPE_VEC2_TC_RGBA   = 0x10082021,   // xyuvrgba xyuvrgba xyuvrgba
+    GPUBUFTYPE_VEC2_TC_RGBA   = 0x10082021,  // xyuvrgba xyuvrgba xyuvrgba
+    GPUBUFTYPE_VEC2_RGBA      = 0x08001821,  // xyrgba xyrgba xyrgba
     //                            ccoossnt
-    GPUBUFTYPE_VEC2_TC_RGBA_BUT_NO_COLOR = GPUBUFTYPE_VEC2_TC_RGBA & 0xffffff,
     GPUBUFTYPE_UVEC2          = 0x00000420
 };
 
@@ -59,6 +59,7 @@ public:
     void *beginWrite(BufDataType type, size_t newsize, unsigned access); // AccessFlags
     bool commitWrite(); // used same size as passed to beginWrite()
     bool commitWrite(size_t used); // explicitly specify used size (may be less than initially requested)
+    bool commitWriteExact(const void *p); // asserts that as many bytes as allocated were written
 
     void upload(BufDataType type, const void *data, size_t size);