MYST3: Improve the node transition performance

On 4K displays, taking a screenshot and processing the pixels on the CPU
was taking a noticeable amount of time. Now the screenshot is copied
directly to a texture without going through the CPU.

engines/myst3/gfx.cpp

@@ -95,6 +95,17 @@ void Renderer::freeFont() {
 	}
 }
 
+Texture *Renderer::copyScreenshotToTexture() {
+	Graphics::Surface *surface = getScreenshot();
+
+	Texture *texture = createTexture(surface);
+
+	surface->free();
+	delete surface;
+
+	return texture;
+}
+
 Common::Rect Renderer::getFontCharacterRect(uint8 character) {
 	uint index = 0;
 

engines/myst3/gfx.h

@@ -137,6 +137,7 @@ public:
 	virtual void draw2DText(const Common::String &text, const Common::Point &position) = 0;
 
 	virtual Graphics::Surface *getScreenshot() = 0;
+	virtual Texture *copyScreenshotToTexture();
 
 	/** Render a Drawable in the specified window */
 	void renderDrawable(Drawable *drawable, Window *window);

engines/myst3/gfx_opengl.cpp

@@ -168,10 +168,14 @@ void OpenGLRenderer::drawTexturedRect2D(const Common::Rect &screenRect, const Co
 	const float tTop = textureRect.top / (float)glTexture->internalHeight;
 	const float tHeight = textureRect.height() / (float)glTexture->internalHeight;
 
-	const float sLeft = screenRect.left;
+	float sLeft = screenRect.left;
-	const float sTop = screenRect.top;
+	float sTop = screenRect.top;
-	const float sWidth = screenRect.width();
+	float sRight = sLeft + screenRect.width();
-	const float sHeight = screenRect.height();
+	float sBottom = sTop + screenRect.height();
+
+	if (glTexture->upsideDown) {
+		SWAP(sTop, sBottom);
+	}
 
 	if (transparency >= 0.0) {
 		if (additiveBlending) {
@@ -192,16 +196,16 @@ void OpenGLRenderer::drawTexturedRect2D(const Common::Rect &screenRect, const Co
 	glBindTexture(GL_TEXTURE_2D, glTexture->id);
 	glBegin(GL_TRIANGLE_STRIP);
 		glTexCoord2f(tLeft, tTop + tHeight);
-		glVertex3f(sLeft + 0, sTop + sHeight, 1.0f);
+		glVertex3f(sLeft + 0, sBottom, 1.0f);
 
 		glTexCoord2f(tLeft + tWidth, tTop + tHeight);
-		glVertex3f(sLeft + sWidth, sTop + sHeight, 1.0f);
+		glVertex3f(sRight, sBottom, 1.0f);
 
 		glTexCoord2f(tLeft, tTop);
 		glVertex3f(sLeft + 0, sTop + 0, 1.0f);
 
 		glTexCoord2f(tLeft + tWidth, tTop);
-		glVertex3f(sLeft + sWidth, sTop + 0, 1.0f);
+		glVertex3f(sRight, sTop + 0, 1.0f);
 	glEnd();
 
 	glDisable(GL_BLEND);
@@ -328,6 +332,15 @@ Graphics::Surface *OpenGLRenderer::getScreenshot() {
 	return s;
 }
 
+Texture *OpenGLRenderer::copyScreenshotToTexture() {
+	OpenGLTexture *texture = new OpenGLTexture();
+
+	Common::Rect screen = viewport();
+	texture->copyFromFramebuffer(screen);
+
+	return texture;
+}
+
 } // End of namespace Myst3
 
 #endif

engines/myst3/gfx_opengl.h

@@ -55,6 +55,8 @@ public:
 	virtual void draw2DText(const Common::String &text, const Common::Point &position) override;
 
 	virtual Graphics::Surface *getScreenshot() override;
+	Texture *copyScreenshotToTexture() override;
+
 private:
 	void drawFace(uint face, Texture *texture);
 };

engines/myst3/gfx_opengl_shaders.cpp

@@ -249,6 +249,7 @@ void ShaderRenderer::drawTexturedRect2D(const Common::Rect &screenRect, const Co
 	_boxShader->setUniform("verSizeWH", scaled(sWidth, sHeight));
 	_boxShader->setUniform("texOffsetXY", Math::Vector2d(tLeft, tTop));
 	_boxShader->setUniform("texSizeWH", Math::Vector2d(tWidth, tHeight));
+	_boxShader->setUniform("flipY", glTexture->upsideDown);
 
 	glDepthMask(GL_FALSE);
 
@@ -398,6 +399,15 @@ Graphics::Surface *ShaderRenderer::getScreenshot() {
 	return s;
 }
 
+Texture *ShaderRenderer::copyScreenshotToTexture() {
+	OpenGLTexture *texture = new OpenGLTexture();
+
+	Common::Rect screen = viewport();
+	texture->copyFromFramebuffer(screen);
+
+	return texture;
+}
+
 } // End of namespace Myst3
 
 #endif

engines/myst3/gfx_opengl_shaders.h

@@ -56,6 +56,7 @@ public:
 	virtual void draw2DText(const Common::String &text, const Common::Point &position) override;
 
 	virtual Graphics::Surface *getScreenshot() override;
+	Texture *copyScreenshotToTexture() override;
 
 private:
 	void setupQuadEBO();

engines/myst3/gfx_opengl_texture.cpp

@@ -42,10 +42,20 @@ static uint32 upperPowerOfTwo(uint32 v) {
 	return v;
 }
 
+OpenGLTexture::OpenGLTexture() :
+		internalFormat(0),
+		sourceFormat(0),
+		internalWidth(0),
+		internalHeight(0),
+		upsideDown(false) {
+	glGenTextures(1, &id);
+}
+
 OpenGLTexture::OpenGLTexture(const Graphics::Surface *surface) {
 	width = surface->w;
 	height = surface->h;
 	format = surface->format;
+	upsideDown = false;
 
 	// Pad the textures if non power of two support is unavailable
 	if (OpenGLContext.NPOTSupported) {
@@ -90,7 +100,7 @@ void OpenGLTexture::update(const Graphics::Surface *surface) {
 	updatePartial(surface, Common::Rect(surface->w, surface->h));
 }
 
-void OpenGLTexture::updateTexture(const Graphics::Surface* surface, const Common::Rect& rect) {
+void OpenGLTexture::updateTexture(const Graphics::Surface *surface, const Common::Rect &rect) {
 	assert(surface->format == format);
 
 	glBindTexture(GL_TEXTURE_2D, id);
@@ -111,6 +121,28 @@ void OpenGLTexture::updatePartial(const Graphics::Surface *surface, const Common
 	updateTexture(surface, rect);
 }
 
+void OpenGLTexture::copyFromFramebuffer(const Common::Rect &screen) {
+	internalFormat = GL_RGB;
+	width  = screen.width();
+	height = screen.height();
+	upsideDown = true;
+
+	// Pad the textures if non power of two support is unavailable
+	if (OpenGLContext.NPOTSupported) {
+		internalHeight = height;
+		internalWidth = width;
+	} else {
+		internalHeight = upperPowerOfTwo(height);
+		internalWidth = upperPowerOfTwo(width);
+	}
+
+	glBindTexture(GL_TEXTURE_2D, id);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+
+	glCopyTexImage2D(GL_TEXTURE_2D, 0, internalFormat, screen.left, screen.top, internalWidth, internalHeight, 0);
+}
+
 } // End of namespace Myst3
 
 #endif

engines/myst3/gfx_opengl_texture.h

@@ -34,16 +34,20 @@ namespace Myst3 {
 class OpenGLTexture : public Texture {
 public:
 	OpenGLTexture(const Graphics::Surface *surface);
+	OpenGLTexture();
 	virtual ~OpenGLTexture();
 
 	void update(const Graphics::Surface *surface) override;
 	void updatePartial(const Graphics::Surface *surface, const Common::Rect &rect) override;
 
+	void copyFromFramebuffer(const Common::Rect &screen);
+
 	GLuint id;
 	GLuint internalFormat;
 	GLuint sourceFormat;
 	uint32 internalWidth;
 	uint32 internalHeight;
+	bool upsideDown;
 
 private:
 	void updateTexture(const Graphics::Surface *surface, const Common::Rect &rect);

engines/myst3/shaders/myst3_box.vertex

@@ -5,6 +5,7 @@ uniform vec2 texOffsetXY;
 uniform vec2 texSizeWH;
 uniform vec2 verOffsetXY;
 uniform vec2 verSizeWH;
+uniform bool flipY;
 
 out vec2 Texcoord;
 
@@ -17,5 +18,9 @@ void main()
 	pos.x = pos.x * 2.0 - 1.0;
 	pos.y = -1.0 * (pos.y * 2.0 - 1.0);
 
+	if (flipY) {
+		pos.y *= -1.0;
+	}
+
 	gl_Position = vec4(pos, 0.0, 1.0);
 }

engines/myst3/transition.cpp

@@ -38,19 +38,15 @@ Transition::Transition(Myst3Engine *vm) :
 		_sourceScreenshot(nullptr),
 		_frameLimiter(new FrameLimiter(g_system, ConfMan.getInt("engine_speed"))) {
 
-	int transitionSpeed = ConfMan.getInt("transition_speed");
-
 	// Capture a screenshot of the source node
-	if (transitionSpeed != 100) {
+	int durationTicks = computeDuration();
-		_sourceScreenshot = _vm->_gfx->getScreenshot();
+	if (durationTicks) {
+		_sourceScreenshot = _vm->_gfx->copyScreenshotToTexture();
 	}
 }
 
 Transition::~Transition() {
-	if (_sourceScreenshot) {
+	_vm->_gfx->freeTexture(_sourceScreenshot);
-		_sourceScreenshot->free();
-		delete _sourceScreenshot;
-	}
 
 	delete _frameLimiter;
 }
@@ -87,13 +83,7 @@ void Transition::draw(TransitionType type) {
 
 	// Capture a screenshot of the destination node
 	_vm->drawFrame(true);
-	Graphics::Surface *target = _vm->_gfx->getScreenshot();
+	Texture *targetScreenshot = _vm->_gfx->copyScreenshotToTexture();
-
-	Texture *sourceTexture = _vm->_gfx->createTexture(_sourceScreenshot);
-	Texture *targetTexture = _vm->_gfx->createTexture(target);
-
-	target->free();
-	delete target;
 
 	// Compute the start and end frames for the animation
 	int startTick = _vm->_state->getTickCount();
@@ -109,7 +99,9 @@ void Transition::draw(TransitionType type) {
 
 		completion = CLIP<int>(100 * (_vm->_state->getTickCount() - startTick) / durationTicks, 0, 100);
 
-		drawStep(targetTexture, sourceTexture, completion);
+		_vm->_gfx->clear();
+
+		drawStep(targetScreenshot, _sourceScreenshot, completion);
 
 		_vm->_gfx->flipBuffer();
 		_frameLimiter->delayBeforeSwap();
@@ -132,8 +124,9 @@ void Transition::draw(TransitionType type) {
 		}
 	}
 
-	_vm->_gfx->freeTexture(sourceTexture);
+	_vm->_gfx->freeTexture(targetScreenshot);
-	_vm->_gfx->freeTexture(targetTexture);
+	_vm->_gfx->freeTexture(_sourceScreenshot);
+	_sourceScreenshot = nullptr;
 }
 
 void Transition::drawStep(Texture *targetTexture, Texture *sourceTexture, uint completion) {

engines/myst3/transition.h

@@ -47,7 +47,7 @@ private:
 	FrameLimiter *_frameLimiter;
 	TransitionType _type;
 
-	Graphics::Surface *_sourceScreenshot;
+	Texture *_sourceScreenshot;
 
 };