3D OpenGL Engine

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Leadwerks

I added a routine that automatically compiles GLLists, the same kind of thing Blitz3D does. Any command that changes a mesh also pokes a value of 1 to DEIMOS_ENTITY_CHANGED. If the rendering routine finds this value, it recompiles the mesh and pokes a value of 0, so that it doesn't get recompiled again.

From deimos\camera.bb:

Function RenderMesh(entity)
list=PeekInt(entity,DEIMOS_ENTITY_GLLIST)

;If mesh has changed, recompile list
If PeekInt(entity,DEIMOS_ENTITY_CHANGED)

	PokeInt entity,DEIMOS_ENTITY_CHANGED,0

	;delete old list
	If list glDeleteLists list,1

	;start new list
	list=glGenLists(1)
	glNewList list,GL_COMPILE
	bank=CreateBank(4)
	PokeInt bank,0,0
	glGetIntegerv(GL_LIST_INDEX,bank)
	FreeBank bank
	PokeInt entity,DEIMOS_ENTITY_GLLIST,list

	;Add all drawing commands to the list
	glBegin GL_TRIANGLES
	For t=1 To CountTriangles(entity)
		For c=1 To 3
			geometryvertex=TriangleVertex(entity,t,c,0)
			colorvertex=TriangleVertex(entity,t,c,1)
			normalvertex=TriangleVertex(entity,t,c,2)
			x#=VertexX(entity,geometryvertex)
			y#=VertexY(entity,geometryvertex)
			z#=VertexZ(entity,geometryvertex)
			vr#=VertexX(entity,colorvertex,1)/255.0
			vg#=VertexY(entity,colorvertex,1)/255.0
			vb#=VertexZ(entity,colorvertex,1)/255.0
			glColor3f vr,vg,vb
			glVertex3f x,y,z
			Next
		Next
	glEnd
	glEndList
	EndIf

;Call gllist (actual drawing)
glPushMatrix
BuildCoordinateSystem(entity)
glCallList list
glPopMatrix

Now it looks like GL vertex arrays are just pointers to vertex lists stored in order. That's easy, and they can be changed without recompiling the mesh.

What is the difference between GLDrawElements and GLDrawArrays?