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Soundbomber's picture

T2 structure

Posted Wednesday, 10 June, 2009 - 14:08 by Soundbomber in

I have just changed to version 0.9.8 and am having a couple of problems.
When passing data to my buffers the BufferData command which worked fine before is throwing errors.

oGL.BufferData(BufferTarget.ArrayBuffer, oObject.oSolidVertices.Length * 12 * _
      Marshal.SizeOf(GetType(UInteger)), oObject.oSolidVertices, BufferUsageHint.DynamicDraw)

The data argument seems to be expecting data in the T2 structure format.
What is the T2 structure? I am currently passing in a custom Vertex structure - can I still do this?

‹ FBO Timer? ›

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the Fiddler's picture

Re: T2 structure

Posted Wednesday, 10 June, 2009 - 16:21 by the Fiddler

Yes, as long as Vertex is a struct, not a class:

struct Vertex { ... }

You can either pass a reference to a single struct or arrays of structures. How is oObject.SolidVertices defined?

Soundbomber's picture

Re: T2 structure

Posted Thursday, 11 June, 2009 - 07:30 by Soundbomber 
Public oSolidVertices() As Vertex
 
Public Structure Vertex
 
        ' Mimic InterleavedArrayFormat.T2fC4fN3fV3f
 
        Public Texture As Vector2
        Public Color As Color4
        Public Normal As Vector3
        Public Position As Vector3
 
End Structure
objarni's picture

Re: T2 structure

Posted Thursday, 11 June, 2009 - 07:57 by objarni

Is this for VBO objects..? I'm new to these, do you have to declare you own structure to use them properly?

Soundbomber's picture

Re: T2 structure

Posted Thursday, 11 June, 2009 - 08:03 by Soundbomber

Yes I'm using VBO's. As far as I am aware you can use any custom structure as long as you set the pointers correctly. I have been using this method successfully in v 0.9.5.

objarni's picture

Re: T2 structure

Posted Thursday, 11 June, 2009 - 08:12 by objarni

Thanks. I'll be asking you for guidence when I come to the point of using VBOs in my "Builder"-object idea.

Soundbomber's picture

Re: T2 structure

Posted Thursday, 11 June, 2009 - 08:21 by Soundbomber

I'm still new to OpenGL, but I will gladly assist if I can. It has been a (sometimes) painful learning curve getting to grips with VBO's and OpenGL in general (not having any experience in 3D graphics), but well worth it.

the Fiddler's picture

Re: T2 structure

Posted Thursday, 11 June, 2009 - 08:54 by the Fiddler

Your code should work. What is the error message?

T2 is the name of a generic parameter - the compiler should infer that the actual type is Vertex. This should not be necessary, but you can try to write:

oGL.BufferData(Of Vertex)(BufferTarget.ArrayBuffer, oObject.oSolidVertices.Length * 12 * _
      Marshal.SizeOf(GetType(UInteger)), oObject.oSolidVertices, BufferUsageHint.DynamicDraw)
Soundbomber's picture

Re: T2 structure

Posted Thursday, 11 June, 2009 - 09:34 by Soundbomber

Using (Of Vertex) for the ArrayBuffer and (Of UShort) for the ElementArrayBuffer did the trick.
I also had to declare the size as an IntPtr object first and then pass that into the argument thus:

        For Each oObject As Model_3DObject In Me.o3DModelObjects
            Dim oVertexSize As IntPtr = oObject.oSolidVertices.Length * 12 * _
                   Marshal.SizeOf(GetType(UInteger))
            Dim oIndexSize As IntPtr = oObject.oSolidIndices.Length * Marshal.SizeOf(GetType(UShort))
            If Not oObject.oSolidVertices Is Nothing And Not oObject.oSolidIndices Is Nothing Then
                oGL.BindBuffer(BufferTarget.ArrayBuffer, Me.oBuffers(iCount))
                oGL.BufferData(Of Vertex)(BufferTarget.ArrayBuffer, oVertexSize, _
                    oObject.oSolidVertices, BufferUsageHint.DynamicDraw)
                iCount += 1
                oGL.BindBuffer(BufferTarget.ElementArrayBuffer, Me.oBuffers(iCount))
                oGL.BufferData(Of UShort)(BufferTarget.ElementArrayBuffer, oIndexSize, _
                    oObject.oSolidIndices, BufferUsageHint.DynamicDraw)
                iCount += 1
            End If
            oVertexSize = oObject.oWireVertices.Length * 12 * Marshal.SizeOf(GetType(UInteger))
            oIndexSize = oObject.oWireLineIndices.Length * Marshal.SizeOf(GetType(UShort))
            If Not oObject.oWireVertices Is Nothing And Not oObject.oWireLineIndices Is Nothing Then
                oGL.BindBuffer(BufferTarget.ArrayBuffer, Me.oBuffers(iCount))
                oGL.BufferData(Of Vertex)(BufferTarget.ArrayBuffer, oVertexSize, oObject.oWireVertices, _
                    BufferUsageHint.DynamicDraw)
                iCount += 1
                oGL.BindBuffer(BufferTarget.ElementArrayBuffer, Me.oBuffers(iCount))
                oGL.BufferData(Of UShort)(BufferTarget.ElementArrayBuffer, oIndexSize, _
                    oObject.oWireLineIndices, BufferUsageHint.DynamicDraw)
                iCount += 1
            End If
        Next

Thank you for the help.