2D graphics with Direct3D

Question

I'm trying to work with 2D graphics using Direct3D 9, but am not sure where to start. Right now I'm using a texture as the "draw buffer", and drawing that texture to screen. For the simplest things, it works. But I can't see a way to e.g. draw lines, arcs, and the like onto the texture. How should I go about doing this?

Answer 1

The GDI approach:

• Create a bitmap and a device context
• Render your 3d graphics into the bitmap using GDI
• StretchBlit the bitmap onto the texture

The Pixel approach:

• Lock the texture and fill the pixels using e.g. Bresenham's algorithm.

The Render approach:

• Use DrawPrimitiveUP with D3DPT_LINELIST or D3DPT_LINESTRIP for drawing lines.

• Arcs, circles and other curved shapes can be composited from lines.

• For filled shapes generate meshes using D3DXCreateShpere/Box/Torus etc. and render those using orthographic projection. You'd use a sphere mesh to render filled circles, a box mesh for filled rectangles and a torus would allow for curved shape outlines.

Answer 2

Use Sprites in Direct3D 9. Very simple way of creating 2D objects in a 3D space.

There's a tutorial here: Sprite Tutorial

I've used sprites to create a 2D HUD in my 3D games and they turn out pretty well.

To draw lines, just use the D3DPT_LINELIST or D3DPT_LINESTRIP primitives with DrawPrimitive().

Drawing Arcs might be a little bit more difficult. You could look into drawing Bezier curves for that: Bezier Curves