From: Steinar H. Gunderson <sgunderson@bigfoot.com>
Date: Thu, 4 Oct 2012 13:53:30 +0000 (+0200)
Subject: Rename needs_many_samples() to needs_texture_bounce(), and update the comment.
X-Git-Tag: 1.0~390
X-Git-Url: https://git.sesse.net/?p=movit;a=commitdiff_plain;h=f23c7768e6c13d6a719aaea89074d86b74148aeb

Rename needs_many_samples() to needs_texture_bounce(), and update the comment.
---

diff --git a/blur_effect.h b/blur_effect.h
index 0c7dccc..3f86e17 100644
--- a/blur_effect.h
+++ b/blur_effect.h
@@ -24,7 +24,7 @@ public:
 		assert(false);
 	}
 
-	virtual bool needs_many_samples() const { return true; }
+	virtual bool needs_texture_bounce() const { return true; }
 	virtual bool needs_mipmaps() const { return true; }
 	virtual void add_self_to_effect_chain(std::vector<Effect *> *chain);
 	virtual bool set_float(const std::string &key, float value);
@@ -38,7 +38,7 @@ public:
 	SingleBlurPassEffect();
 	std::string output_fragment_shader();
 
-	virtual bool needs_many_samples() const { return true; }
+	virtual bool needs_texture_bounce() const { return true; }
 	virtual bool needs_mipmaps() const { return true; }
 
 	void set_uniforms(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num);
diff --git a/effect.h b/effect.h
index f495867..4191d4d 100644
--- a/effect.h
+++ b/effect.h
@@ -49,7 +49,7 @@ public:
 	// the pixels, e.g. mirror, won't need to care, and can set this
 	// to false. If so, the input gamma will be undefined.
 	//
-	// Also see the note on needs_many_samples(), below.
+	// Also see the note on needs_texture_bounce(), below.
 	virtual bool needs_linear_light() const { return true; }
 
 	// Whether this effect expects its input to be in the sRGB
@@ -61,19 +61,29 @@ public:
 	// Again, most effects will want this.
 	virtual bool needs_srgb_primaries() const { return true; }
 
-	// Whether this effect expects to be sampling many times from
-	// its input. If this is true, the framework will not chain the
+	// Whether this effect expects its input to come directly from
+	// a texture. If this is true, the framework will not chain the
 	// input from other effects, but will store the results of the
 	// chain to a temporary (RGBA fp16) texture and let this effect
 	// sample directly from that.
 	//
-	// Note that if you do _not_ set this, and do not sample on
-	// whole pixels (ie. you request linear filtering), it is undefined
-	// whether that filtering happen in linear gamma or not.
-	// It _could_ be (for instance in the case where the input is sRGB
-	// and your GPU applies gamma expansion before filtering), but you
-	// have no such guarantee. For most uses, however, this will be fine.
-	virtual bool needs_many_samples() const { return false; }
+	// There are two good reasons why you might want to set this:
+	//
+	//  1. You are sampling more than once from the input,
+	//     in which case computing all the previous steps might
+	//     be more expensive than going to a memory intermediate.
+	//  2. You rely on previous effects, possibly including gamma
+	//     expansion, to happen pre-filtering instead of post-filtering.
+	//     (This is only relevant if you actually need the filtering; if
+	//     you sample on whole input pixels only, it makes no difference.)
+	//
+	// Note that in some cases, you might get post-filtered gamma expansion
+	// even when setting this option. More specifically, if you are the
+	// first effect in the chain, and the GPU is doing sRGB gamma
+	// expansion, it is undefined (from OpenGL's side) whether expansion
+	// happens pre- or post-filtering. For most uses, however,
+	// either will be fine.
+	virtual bool needs_texture_bounce() const { return false; }
 
 	// Whether this effect expects mipmaps or not. If you set this to
 	// true, you will be sampling with bilinear filtering; if not,
diff --git a/effect_chain.cpp b/effect_chain.cpp
index e728963..fcf94f8 100644
--- a/effect_chain.cpp
+++ b/effect_chain.cpp
@@ -208,7 +208,7 @@ void EffectChain::finalize()
 	// and of course at the end.
 	unsigned start = 0;
 	for (unsigned i = 0; i < effects.size(); ++i) {
-		if (effects[i]->needs_many_samples() && i != start) {
+		if (effects[i]->needs_texture_bounce() && i != start) {
 			phases.push_back(compile_glsl_program(start, i));
 			start = i;
 		}
diff --git a/main.cpp b/main.cpp
index abc0a38..b41c9ed 100644
--- a/main.cpp
+++ b/main.cpp
@@ -150,7 +150,7 @@ int main(int argc, char **argv)
 	glPixelStorei(GL_PACK_ALIGNMENT, 1);
 
 	unsigned img_w, img_h;
-	unsigned char *src_img = load_image("blg_wheels_woman_1.jpg", &img_w, &img_h);
+	unsigned char *src_img = load_image("test.jpg", &img_w, &img_h);
 
 	EffectChain chain(WIDTH, HEIGHT);