3D Vertex to 2D render target co-ordinates

Hi, y'all,

I'm having a small problem using DirectX7.
I am creating a modeller application and use a VB form as the render target. If, for example, I render a simple primitive, such as a triangle, to the form, I want to be able to click on the primitive and then use GDI to place a 'selected' indication with node points for dragging. This works, but I find that when I cycle through the vertices of the primitive and perform manual World, View and Projection transformations (and a final 'flatten' matrix to convert using homogenous-w) the 'selected' indication is offset slightly from the original DirectX rendered primitive (i.e I end up with TWO triangles on the render target).

Does anyone have some example code (NOT Retained Mode, but Immediate Mode) to help a poor DirectX beginner obtain the correct x,y co-ordinates (i.e the same as DirectX before it is passed to the Rasterizer)?

Any help would be GREATLY appreciated!

Grrr... It would be easier with DX8, there are built in functions for this =).

There might be a bug in your transformation code itself. I would also do a google search for Something along the lines of "Project D3D7 Immediate". That should turn up quite a few hits.

Good luck.

Z.

I'm aware that DX8 has functions for this, but since I'm using the DX7 SDK at the moment (and still getting to grips with things 3D), I wanted to have a crack with my existing set up.

I must agree that the problem must lie in the transformations I'm applying, but the matrices are pulled from the DX7 SDK help and leave me but a few pixels out in both x and y co-ords.

Hence the reason I'm searching for some example code.

Thanks for looking though!