modules/roto: drive from ticks, move palette to contetxt

The palette mutates across frames, on a context-specific
schedule.  Meaning the palette is per-context, so move it into
roto_context_t.

The phase also needs to be driven by ticks.  And when ticks
doesn't change in cases where the same context is rendered
manifold in the same frame, the phase shouldn't move.

1 files changed, 20 insertions, 16 deletions

diff --git a/src/modules/roto/roto.c b/src/modules/roto/roto.c
index 389aa5d..1831d2b 100644
--- a/src/modules/roto/roto.c
+++ b/src/modules/roto/roto.c
@@ -27,11 +27,11 @@ typedef struct color_t {
 typedef struct roto_context_t {
 	til_module_context_t	til_module_context;
 	unsigned		r, rr;
+	color_t			palette[2];
 } roto_context_t;
 
 static int32_t	costab[FIXED_TRIG_LUT_SIZE], sintab[FIXED_TRIG_LUT_SIZE];
 static uint8_t	texture[256][256];
-static color_t	palette[2];
 
 static til_module_context_t * roto_create_context(unsigned seed, unsigned ticks, unsigned n_cpus, til_setup_t *setup)
 {
@@ -125,9 +125,9 @@ static uint32_t bilerp_color(uint8_t texture[256][256], color_t *palette, int tx
 
 	/* Skip interpolation of same colors, a substantial optimization with plain textures like the checker pattern */
 	if (nw == ne) {
-		if (ne == sw && sw == se) {
+		if (ne == sw && sw == se)
 			return (FIXED_TO_INT(palette[sw].r) << 16) | (FIXED_TO_INT(palette[sw].g) << 8) | FIXED_TO_INT(palette[sw].b);
-		}
+
 		n_color = palette[nw];
 	} else {
 		n_color = lerp_color(&palette[nw], &palette[ne], x_alpha);
@@ -188,8 +188,21 @@ static void roto_prepare_frame(til_module_context_t *context, unsigned ticks, ti
 	*res_fragmenter = til_fragmenter_slice_per_cpu;
 
 	// This governs the rotation and color cycle.
-	ctxt->r += FIXED_TO_INT(FIXED_MULT(FIXED_SIN(ctxt->rr), FIXED_NEW(16)));
-	ctxt->rr += 2;
+	if (ticks != context->ticks) {
+		ctxt->r += FIXED_TO_INT(FIXED_MULT(FIXED_SIN(ctxt->rr), FIXED_NEW(16)));
+		ctxt->rr += (ticks - context->ticks) >> 2;
+
+		/* Vary the colors, this is just a mashup of sinusoidal rgb values. */
+		ctxt->palette[0].r = (FIXED_MULT(FIXED_COS(ctxt->rr), FIXED_NEW(127)) + FIXED_NEW(128));
+		ctxt->palette[0].g = (FIXED_MULT(FIXED_SIN(ctxt->rr / 2), FIXED_NEW(127)) + FIXED_NEW(128));
+		ctxt->palette[0].b = (FIXED_MULT(FIXED_COS(ctxt->rr / 3), FIXED_NEW(127)) + FIXED_NEW(128));
+
+		ctxt->palette[1].r = (FIXED_MULT(FIXED_SIN(ctxt->rr / 2), FIXED_NEW(127)) + FIXED_NEW(128));
+		ctxt->palette[1].g = (FIXED_MULT(FIXED_COS(ctxt->rr / 2), FIXED_NEW(127)) + FIXED_NEW(128));
+		ctxt->palette[1].b = (FIXED_MULT(FIXED_SIN(ctxt->rr), FIXED_NEW(127)) + FIXED_NEW(128));
+
+		context->ticks = ticks;
+	}
 }
 
 
@@ -197,8 +210,8 @@ static void roto_prepare_frame(til_module_context_t *context, unsigned ticks, ti
 static void roto_render_fragment(til_module_context_t *context, unsigned ticks, unsigned cpu, til_fb_fragment_t *fragment)
 {
 	roto_context_t	*ctxt = (roto_context_t *)context;
-	int		y_cos_r, y_sin_r, x_cos_r, x_sin_r, x_cos_r_init, x_sin_r_init, cos_r, sin_r;
 	int		x, y, frame_width = fragment->frame_width, frame_height = fragment->frame_height;
+	int		y_cos_r, y_sin_r, x_cos_r, x_sin_r, x_cos_r_init, x_sin_r_init, cos_r, sin_r;
 	uint32_t	*buf = fragment->buf;
 
 	/* This is all done using fixed-point in the hopes of being faster, and yes assumptions
@@ -206,15 +219,6 @@ static void roto_render_fragment(til_module_context_t *context, unsigned ticks,
 	cos_r = FIXED_COS(ctxt->r);
 	sin_r = FIXED_SIN(ctxt->r);
 
-	/* Vary the colors, this is just a mashup of sinusoidal rgb values. */
-	palette[0].r = (FIXED_MULT(FIXED_COS(ctxt->rr), FIXED_NEW(127)) + FIXED_NEW(128));
-	palette[0].g = (FIXED_MULT(FIXED_SIN(ctxt->rr / 2), FIXED_NEW(127)) + FIXED_NEW(128));
-	palette[0].b = (FIXED_MULT(FIXED_COS(ctxt->rr / 3), FIXED_NEW(127)) + FIXED_NEW(128));
-
-	palette[1].r = (FIXED_MULT(FIXED_SIN(ctxt->rr / 2), FIXED_NEW(127)) + FIXED_NEW(128));
-	palette[1].g = (FIXED_MULT(FIXED_COS(ctxt->rr / 2), FIXED_NEW(127)) + FIXED_NEW(128));
-	palette[1].b = (FIXED_MULT(FIXED_SIN(ctxt->rr), FIXED_NEW(127)) + FIXED_NEW(128));
-
 	/* The dimensions are cut in half and negated to center the rotation. */
 	/* The [xy]_{sin,cos}_r variables are accumulators to replace multiplication with addition. */
 	x_cos_r_init = FIXED_MULT(-FIXED_NEW(frame_width / 2) + FIXED_NEW(fragment->x), cos_r);
@@ -229,7 +233,7 @@ static void roto_render_fragment(til_module_context_t *context, unsigned ticks,
 		x_sin_r = x_sin_r_init;
 
 		for (x = fragment->x; x < fragment->x + fragment->width; x++, buf++) {
-			*buf = bilerp_color(texture, palette, x_sin_r - y_cos_r, y_sin_r + x_cos_r);
+			*buf = bilerp_color(texture, ctxt->palette, x_sin_r - y_cos_r, y_sin_r + x_cos_r);
 
 			x_cos_r += cos_r;
 			x_sin_r += sin_r;