obs-transitions: Implement fade transition

A basic fade transition that fades to/from a source via a simple cross
fade.

plugins/obs-transitions/CMakeLists.txt

@@ -0,0 +1,13 @@
+project(obs-transitions)
+
+set(obs-transitions_SOURCES
+	obs-transitions.c
+	transition-fade.c
+	)
+
+add_library(obs-transitions MODULE
+	${obs-transitions_SOURCES})
+target_link_libraries(obs-transitions
+	libobs)
+
+install_obs_plugin_with_data(obs-transitions data)

plugins/obs-transitions/data/fade_transition.effect

@@ -0,0 +1,39 @@
+uniform float4x4 ViewProj;
+uniform texture2d tex_a;
+uniform texture2d tex_b;
+uniform float fade_val;
+
+sampler_state textureSampler {
+	Filter    = Linear;
+	AddressU  = Clamp;
+	AddressV  = Clamp;
+};
+
+struct VertData {
+	float4 pos : POSITION;
+	float2 uv  : TEXCOORD0;
+};
+
+VertData VSDefault(VertData v_in)
+{
+	VertData vert_out;
+	vert_out.pos = mul(float4(v_in.pos.xyz, 1.0), ViewProj);
+	vert_out.uv  = v_in.uv;
+	return vert_out;
+}
+
+float4 PSFade(VertData v_in) : TARGET
+{
+	float4 a_val = tex_a.Sample(textureSampler, v_in.uv);
+	float4 b_val = tex_b.Sample(textureSampler, v_in.uv);
+	return lerp(a_val, b_val, fade_val);
+}
+
+technique Fade
+{
+	pass
+	{
+		vertex_shader = VSDefault(v_in);
+		pixel_shader = PSFade(v_in);
+	}
+}

plugins/obs-transitions/data/locale/en-US.ini

@@ -0,0 +1 @@
+FadeTransition="Fade"

plugins/obs-transitions/obs-transitions.c

@@ -0,0 +1,13 @@
+#include <obs-module.h>
+
+OBS_DECLARE_MODULE()
+
+OBS_MODULE_USE_DEFAULT_LOCALE("obs-transitions", "en-US")
+
+extern struct obs_source_info fade_transition;
+
+bool obs_module_load(void)
+{
+	obs_register_source(&fade_transition);
+	return true;
+}

plugins/obs-transitions/transition-fade.c

@@ -0,0 +1,100 @@
+#include <obs-module.h>
+
+struct fade_info {
+	obs_source_t *source;
+
+	gs_effect_t *effect;
+	gs_eparam_t *a_param;
+	gs_eparam_t *b_param;
+	gs_eparam_t *fade_param;
+};
+
+static const char *fade_get_name(void *type_data)
+{
+	UNUSED_PARAMETER(type_data);
+	return obs_module_text("FadeTransition");
+}
+
+void *fade_create(obs_data_t *settings, obs_source_t *source)
+{
+	struct fade_info *fade;
+	char *file = obs_module_file("fade_transition.effect");
+	gs_effect_t *effect;
+
+	obs_enter_graphics();
+	effect = gs_effect_create_from_file(file, NULL);
+	obs_leave_graphics();
+	bfree(file);
+
+	if (!effect) {
+		blog(LOG_ERROR, "Could not find fade_transition.effect");
+		return NULL;
+	}
+
+	fade = bmalloc(sizeof(*fade));
+	fade->source = source;
+	fade->effect = effect;
+	fade->a_param = gs_effect_get_param_by_name(effect, "tex_a");
+	fade->b_param = gs_effect_get_param_by_name(effect, "tex_b");
+	fade->fade_param = gs_effect_get_param_by_name(effect, "fade_val");
+
+	UNUSED_PARAMETER(settings);
+	return fade;
+}
+
+void fade_destroy(void *data)
+{
+	struct fade_info *fade = data;
+	bfree(fade);
+}
+
+static void fade_callback(void *data, gs_texture_t *a, gs_texture_t *b, float t,
+		uint32_t cx, uint32_t cy)
+{
+	struct fade_info *fade = data;
+
+	gs_effect_set_texture(fade->a_param, a);
+	gs_effect_set_texture(fade->b_param, b);
+	gs_effect_set_float(fade->fade_param, t);
+
+	while (gs_effect_loop(fade->effect, "Fade"))
+		gs_draw_sprite(NULL, 0, cx, cy);
+}
+
+void fade_video_render(void *data, gs_effect_t *effect)
+{
+	struct fade_info *fade = data;
+	obs_transition_video_render(fade->source, fade_callback);
+	UNUSED_PARAMETER(effect);
+}
+
+static float mix_a(void *data, float t)
+{
+	UNUSED_PARAMETER(data);
+	return 1.0f - t;
+}
+
+static float mix_b(void *data, float t)
+{
+	UNUSED_PARAMETER(data);
+	return t;
+}
+
+bool fade_audio_render(void *data, uint64_t *ts_out,
+		struct obs_source_audio_mix *audio, uint32_t mixers,
+		size_t channels, size_t sample_rate)
+{
+	struct fade_info *fade = data;
+	return obs_transition_audio_render(fade->source, ts_out,
+		audio, mixers, channels, sample_rate, mix_a, mix_b);
+}
+
+struct obs_source_info fade_transition = {
+	.id = "fade_transition",
+	.type = OBS_SOURCE_TYPE_TRANSITION,
+	.get_name = fade_get_name,
+	.create = fade_create,
+	.destroy = fade_destroy,
+	.video_render = fade_video_render,
+	.audio_render = fade_audio_render
+};