Master of Puppets

Location

include/mop/postprocess.h     — Public API
src/postprocess/postprocess.c  — Per-pixel effect loops

Overview

Post-processing effects are applied to the framebuffer after all geometry has been rendered. Effects are controlled by a bitmask and applied in a fixed order: fog, tonemapping, gamma correction, vignette.

Effects

MopPostEffect

typedef enum MopPostEffect {
    MOP_POST_NONE     = 0,
    MOP_POST_GAMMA    = 1 << 0,
    MOP_POST_TONEMAP  = 1 << 1,
    MOP_POST_VIGNETTE = 1 << 2,
    MOP_POST_FOG      = 1 << 3
} MopPostEffect;

Effects can be combined with bitwise OR:

mop_viewport_set_post_effects(vp, MOP_POST_GAMMA | MOP_POST_TONEMAP);

Effect Details

Effect	Algorithm	Notes
`MOP_POST_FOG`	Linear depth fog: `mix(color, fog_color, t)` where `t = (depth - near) / (far - near)`	Requires `mop_viewport_set_fog()` to set color and distance range
`MOP_POST_TONEMAP`	Reinhard: `c / (c + 1)`	Applied per-channel in linear space
`MOP_POST_GAMMA`	`pow(c, 1/2.2)`	sRGB gamma correction
`MOP_POST_VIGNETTE`	Darkens edges based on distance from center	Quadratic falloff, 20% darkening at corners

Application Order

When multiple effects are enabled, they are applied in this order:

Fog — blends geometry with fog color based on depth
Tonemap — compresses HDR to [0,1] range
Gamma — converts linear to sRGB
Vignette — artistic edge darkening

Functions

mop_viewport_set_post_effects

void mop_viewport_set_post_effects(MopViewport *viewport, uint32_t effects);

Sets the active post-processing effects. Pass MOP_POST_NONE (0) to disable all. Effects take effect on the next mop_viewport_render call.

mop_viewport_set_fog

void mop_viewport_set_fog(MopViewport *viewport, const MopFogParams *fog);

Configures fog parameters. Only used when MOP_POST_FOG is enabled.

MopFogParams

typedef struct MopFogParams {
    MopColor color;       /* Fog color (typically matches clear color) */
    float    near_dist;   /* Depth where fog begins (0 = camera)      */
    float    far_dist;    /* Depth where fog is fully opaque           */
} MopFogParams;

Usage Example

/* Enable gamma correction and fog */
mop_viewport_set_post_effects(vp, MOP_POST_GAMMA | MOP_POST_FOG);
mop_viewport_set_fog(vp, &(MopFogParams){
    .color     = { 0.6f, 0.7f, 0.8f, 1.0f },
    .near_dist = 5.0f,
    .far_dist  = 50.0f
});