&globe &globe v2

native/main.cpp

@@ -218,29 +218,36 @@ int main() {
 	}
 
 	glClearColor(0.25, 0.25, 0.25, 1);
-	glClear(GL_COLOR_BUFFER_BIT);
 	glEnable(GL_BLEND);
 	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
-	const float increment = -1.0f/30.0f;
-	float offset = 0;
-	while (!glfwWindowShouldClose(window)) {
-		glUniform1f(glGetUniformLocation(shader.id, "aHorizontalOffset"), offset);
-		offset += increment;
-		if (offset <= -1)
-			offset = 0;
 
+	glBindFramebuffer(GL_FRAMEBUFFER, frameBuffer);
+	glClear(GL_COLOR_BUFFER_BIT);
+
+	const float increment = -1.0f/60.0f;
+	float globe0Offset = 0;
+	float globe1Offset = 0;
+	while (!glfwWindowShouldClose(window)) {
 		glBindFramebuffer(GL_FRAMEBUFFER, frameBuffer);
-		glUniform1f(glGetUniformLocation(shader.id, "aTexCoordYScale"), -1);
+		glUniform1f(glGetUniformLocation(shader.id, "aTexCoordYScale"), 1);
+		glUniform1f(glGetUniformLocation(shader.id, "aHorizontalOffset"), globe0Offset);
 		glActiveTexture(GL_TEXTURE0);
 		glBindTexture(GL_TEXTURE_2D, texture);
 		square.draw();
 
 		glBindFramebuffer(GL_FRAMEBUFFER, 0);
-		glUniform1f(glGetUniformLocation(shader.id, "aTexCoordYScale"), 1);
 		glClear(GL_COLOR_BUFFER_BIT);
+		glUniform1f(glGetUniformLocation(shader.id, "aTexCoordYScale"), -1);
+		glUniform1f(glGetUniformLocation(shader.id, "aHorizontalOffset"), globe1Offset);
 		glActiveTexture(GL_TEXTURE0);
 		glBindTexture(GL_TEXTURE_2D, colorBuffer);
 		square.draw();
+
+		globe0Offset += increment;
+		if (globe0Offset <= -2)
+			globe0Offset = 0;
+		globe1Offset = globe0Offset * 0.5f;
+
 		glfwSwapBuffers(window);
 		glfwPollEvents();
 	}

shaders/fragment.glsl

@@ -17,9 +17,19 @@
 #version 330 core
 
 in vec2 vFragCoord;
-
-uniform float aHorizontalOffset;
+in vec2 vTexCoord;
 uniform sampler2D aTexture;
+uniform float aHorizontalOffset;
+
+// Set to 1 or -1 to flip Y
+uniform float aTexCoordYScale;
+
+// Adds the Z value to a vec2, calculating it assuming
+// it's a sphere with a radius of 2
+vec3 getZInSphere(vec2 v) {
+	const float radius = 2;
+	return vec3(v, sqrt(radius-dot(v,v)));
+}
 
 void main() {
 	float distanceFromCenterSquared = dot(vFragCoord, vFragCoord);
@@ -28,10 +38,30 @@ void main() {
 	// alpha = 1 if fragment is inside circle
 	float alpha = distanceFromCenterSquared > 1 ? 0 : 1;
 
-	// An equation which seems to work
-	float specular = distanceFromCenterSquared * (-0.5f*vFragCoord.x + vFragCoord.y) + 1;
+	vec3 normal;
+	{
+		// Form a triangle to approximate the normal or something like that
+		const float offset = 0.001;
+		vec3 p0 = getZInSphere(vFragCoord + vec2(0, offset));
+		vec3 p1 = getZInSphere(vFragCoord + vec2(offset, -offset));
+		vec3 p2 = getZInSphere(vFragCoord + vec2(-offset, -offset));
 
-	vec2 texCoord = vFragCoord * vec2(0.5,0.5) + vec2(0.5+aHorizontalOffset,0.5);
+		// Now calculate the normal of the triangle
+		vec3 a = p0 - p1;
+		vec3 b = p2 - p1;
+		normal = normalize(cross(a, b));
+	}
 
-	gl_FragColor = vec4(texture(aTexture, texCoord).xyz*specular, alpha);
+	const float pi = radians(180);
+	// Based off of https://stackoverflow.com/questions/41957890/how-to-properly-map-a-2d-image-texture-to-an-icosphere
+	vec2 texCoord = vec2(
+		atan(normal.x, normal.z) * (1.0f/pi),
+		asin(-normal.y) * (2.0f/pi) * aTexCoordYScale
+	) + vec2(0.5f+aHorizontalOffset, 0.5f);
+
+	// Some equation which seems to work good enough
+	float specular = (dot(normal, normalize(vec3(-1, 2, 0.5f))) - 0.25f) * 1.3f + 0.1f;
+	specular = specular*specular * sign(specular);
+
+	gl_FragColor = vec4(texture(aTexture, texCoord).rgb + (vec3(1,1,1) * specular), alpha);
 }

shaders/vertex.glsl

@@ -20,10 +20,7 @@ layout (location = 0) in vec2 aPosition;
 
 out vec2 vFragCoord;
 
-// Set to 1 or -1 to flip Y
-uniform float aTexCoordYScale;
-
 void main() {
 	gl_Position = vec4(aPosition, 0, 1);
-	vFragCoord = aPosition * vec2(1, aTexCoordYScale);
+	vFragCoord = aPosition;
 }