/// <summary>
/// Wraps glDrawElements(uint mode, int count, uint type, IntPtr indices).
/// </summary>
/// <param name="bufferId">用glGenBuffers()得到的VBO的Id。<para>Id got from glGenBuffers();</para></param>
/// <param name="mode">用哪种方式渲染各个顶点？（OpenGL.GL_TRIANGLES etc.）</param>
/// <param name="type">type in glDrawElements(uint mode, int count, uint type, IntPtr indices);
/// <para>表示第3个参数，表示索引元素的类型。</para></param>
/// <param name="length">此VBO含有多个个元素？<para>How many elements?</para></param>
/// <param name="byteLength">此VBO中的数据在内存中占用多少个字节？<para>How many bytes in this buffer?</para></param>
/// <param name="primCount">primCount in instanced rendering.</param>
internal OneIndexBufferPtr(uint bufferId, DrawMode mode,
IndexElementType type, int length, int byteLength, int primCount = 1)
: base(mode, bufferId, length, byteLength, primCount)
{
if (glDrawElementsInstanced == null)
{
glDrawElementsInstanced = OpenGL.GetDelegateFor <OpenGL.glDrawElementsInstanced>();
}
this.ElementCount = length;
this.Type = type;
}
/// <summary>
///
/// </summary>
public override void Render()
{
int primCount = this.PrimCount;
if (primCount < 1)
{
throw new Exception("error: primCount is less than 1.");
}
uint mode = (uint)this.Mode;
IntPtr offset;
switch (this.ElementType)
{
case IndexBufferElementType.UByte:
offset = new IntPtr(this.FirstIndex * sizeof(byte));
break;
case IndexBufferElementType.UShort:
offset = new IntPtr(this.FirstIndex * sizeof(ushort));
break;
case IndexBufferElementType.UInt:
offset = new IntPtr(this.FirstIndex * sizeof(uint));
break;
default:
throw new NotImplementedException();
}
if (glBindBuffer == null)
{
glBindBuffer = OpenGL.GetDelegateFor <OpenGL.glBindBuffer>();
}
glBindBuffer(OpenGL.GL_ELEMENT_ARRAY_BUFFER, this.BufferId);
if (primCount == 1)
{
OpenGL.DrawElements(mode, this.ElementCount, (uint)this.ElementType, offset);
}
else
{
if (glDrawElementsInstanced == null)
{
glDrawElementsInstanced = OpenGL.GetDelegateFor <OpenGL.glDrawElementsInstanced>();
}
glDrawElementsInstanced(mode, this.ElementCount, (uint)this.ElementType, offset, primCount);
}
glBindBuffer(OpenGL.GL_ELEMENT_ARRAY_BUFFER, 0);
}
/// <summary>
///
/// </summary>
/// <param name="arg"></param>
public override void Render(RenderEventArgs arg)
{
int primCount = this.PrimCount;
if (primCount < 1)
{
throw new Exception("error: primCount is less than 1.");
}
uint mode = 0;
IntPtr offset;
if (arg.PickingGeometryType == PickingGeometryType.Point &&
this.Mode.ToGeometryType() == PickingGeometryType.Line) // picking point from a line
{
// this may render points that should not appear.
// so need to select by another picking.
mode = (uint)DrawMode.Points;
}
else
{
mode = (uint)this.Mode;
}
switch (this.ElementType)
{
case IndexBufferElementType.UByte:
offset = new IntPtr(this.FirstIndex * sizeof(byte));
break;
case IndexBufferElementType.UShort:
offset = new IntPtr(this.FirstIndex * sizeof(ushort));
break;
case IndexBufferElementType.UInt:
offset = new IntPtr(this.FirstIndex * sizeof(uint));
break;
default:
throw new NotImplementedException();
}
if (glBindBuffer == null)
{
glBindBuffer = OpenGL.GetDelegateFor <OpenGL.glBindBuffer>();
}
glBindBuffer(OpenGL.GL_ELEMENT_ARRAY_BUFFER, this.BufferId);
if (primCount == 1)
{
OpenGL.DrawElements(mode, this.ElementCount, (uint)this.ElementType, offset);
}
else
{
if (glDrawElementsInstanced == null)
{
glDrawElementsInstanced = OpenGL.GetDelegateFor <OpenGL.glDrawElementsInstanced>();
}
glDrawElementsInstanced(mode, this.ElementCount, (uint)this.ElementType, offset, primCount);
}
glBindBuffer(OpenGL.GL_ELEMENT_ARRAY_BUFFER, 0);
}