Why does gpu_set_blendmode affect later draws?

GPU state persists until reset. After your styled draw, call gpu_set_blendmode(bm_normal). Otherwise next draw inherits the additive/subtractive blend.

Save/restore pattern?

var prev = gpu_get_blendmode(); gpu_set_blendmode(bm_add); draw_self(); gpu_set_blendmode(prev). Restores whatever was active.

Same applies to gpu_set_alpha, gpu_set_colorwriteenable, gpu_set_blendenable. Always pair set/reset, or save/restore.

Fix: GameMaker gpu_set_blendmode Bleeds Into Next Draw

Quick answer: Reset with gpu_set_blendmode(bm_normal) after each styled draw. Or save/restore via gpu_get_blendmode().

Glow particle uses bm_add blend. Next sprite drawn afterward uses additive blend too because state wasn't reset.

The Fix

// Save/restore
var _prev = gpu_get_blendmode();
gpu_set_blendmode(bm_add);
draw_sprite(spr_glow, 0, x, y);
gpu_set_blendmode(_prev);

// Or always reset to bm_normal
gpu_set_blendmode(bm_add);
draw_sprite(spr_glow, 0, x, y);
gpu_set_blendmode(bm_normal);

Save/restore handles nested code. Bm_normal reset is the simpler default.

Verifying

Glow draws additive; subsequent sprites draw normal. Without reset: next sprite mistakenly additive.

“Reset state. No bleed.”

Related Issues

For draw text color, see draw color. For shader uniform, see uniform.

Reset blend. Clean draw.