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cf_canvas_copy_depth

Category: graphics
GitHub: cute_graphics.h

Copies the whole depth (and stencil) target of one canvas into another.

void cf_canvas_copy_depth(CF_Canvas dst, CF_Canvas src);
Parameters Description
dst The canvas receiving the depth.
src The canvas whose depth is copied.

Remarks

This is how a pass samples the depth of the canvas it is still depth-testing against: soft particles, water, decals, and SDF occlusion all want both at once, and a texture can't be sampled while attached. Draw the scene, copy its depth, then draw the effects into the scene canvas while they sample the copy.

CF_CanvasParams params = cf_canvas_defaults(w, h);
params.depth_stencil_enable = true;
CF_Canvas scene = cf_make_canvas(params);
params.depth_stencil_target.usage |= CF_TEXTURE_USAGE_SAMPLER_BIT;
params.depth_stencil_target.filter = CF_FILTER_NEAREST;
CF_Canvas scene_depth = cf_make_canvas(params);

// ...draw opaque geometry into `scene`...
cf_canvas_copy_depth(scene_depth, scene);
cf_material_set_texture_fs(fx, "u_depth", cf_canvas_get_depth_stencil_target(scene_depth));
cf_apply_canvas(scene, false);
// ...draw effects with depth testing on, fading against `u_depth`...

Both canvases need a depth target of the same size and format, and neither may use MSAA; anything else asserts, logs to stderr, and copies nothing. Only dst needs CF_TEXTURE_USAGE_SAMPLER_BIT, and only to be sampled. The copy works at canvas level because a depth target without sampler usage may not be a texture at all (a renderbuffer on OpenGL ES). If dst exists only to hold the copy, make it depth-only by attaching a depth texture with attach_target.

Draws submitted through the immediate-mode draw API are copied only after they reach the canvas (cf_render_to). SDL_GPU's D3D12 driver copies only the depth plane, so don't rely on a copied stencil there.

cf_canvas_get_depth_stencil_target
CF_CanvasParams
cf_make_canvas
cf_apply_canvas