From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 13 Dec 2015 11:53:59 +0000 (+0200)
Subject: Use a more 3d-y approach for generating the monitor mesh
X-Git-Url: http://git.tdb.fi/?p=geometrycompositor.git;a=commitdiff_plain;h=6d10193f0bc3827089e919d41fe6af53ffe0e1a7

Use a more 3d-y approach for generating the monitor mesh

It's easier to grasp, especially when more corrections are implemented.

The coordinates for cylinder correction are now spaced evenly by angle
rather than X coordinate.  This also fixes incorrect texture coordinates.
---

diff --git a/source/main.c b/source/main.c
index 04e6620..08be9dd 100644
--- a/source/main.c
+++ b/source/main.c
@@ -465,49 +465,75 @@ void update_monitor_vertices(CompositedScreen *screen, CompositedMonitor *monito
 	unsigned x, y;
 	unsigned i;
 	float aspect;
-	float cyl_w_sq;
+	float cyl_radius;
+	float cyl_arc;
 	float sin_ksv;
 	float cos_ksv;
+	float distance;
+	float eye[3];
+	float look[3];
 
 	t = monitor->tessellation;
 
 	data_size = (t+1)*(t+1)*4*sizeof(float);
 	vertex_data = (float *)malloc(data_size);
+
 	aspect = (float)monitor->width/monitor->height;
-	cyl_w_sq = 0.25f-(0.5f-monitor->cylinder_depth)*(0.5f-monitor->cylinder_depth);
+
+	if(monitor->cylinder_depth)
+	{
+		cyl_radius = (monitor->cylinder_depth*monitor->cylinder_depth+0.25f)/(2.0f*monitor->cylinder_depth);
+		cyl_arc = 2.0f*asin(0.5f/cyl_radius);
+	}
+
 	sin_ksv = monitor->keystone_vertical/sqrt(1.0f+monitor->keystone_vertical*monitor->keystone_vertical);
 	cos_ksv = sqrt(1.0f-sin_ksv*sin_ksv);
+	distance = monitor->perspective+sin_ksv*((sin_ksv>0)-monitor->vertical_center)/aspect;
+
+	eye[0] = 0.0f;
+	eye[1] = (monitor->vertical_center-0.5f)/aspect+sin_ksv*distance;
+	eye[2] = cos_ksv*distance;
+
+	look[0] = 0.0f;
+	look[1] = -sin_ksv;
+	look[2] = -cos_ksv;
+
 	for(y=0; y<=t; ++y)
 		for(x=0; x<=t; ++x)
 		{
-			float xf, yf, z, rz;
-			float scale;
 			float *v;
 
-			xf = (float)x/t;
-			yf = (float)y/t;
-
-			v = vertex_data+(y*(t+1)+x)*4;
-			v[2] = (monitor->x+xf*monitor->width)/screen->width;
-			v[3] = ((float)screen->height-monitor->y-monitor->height+yf*monitor->height)/screen->height;
-
-			z = sqrt(0.25f-(xf-0.5f)*(xf-0.5f)*4.0f*cyl_w_sq)-0.5f+monitor->cylinder_depth;
-			if(monitor->keystone_vertical>0)
+			v = vertex_data+(y*(t+1)+x)*3;
+			v[0] = (float)x/t-0.5f;
+			v[1] = ((float)y/t-0.5f)/aspect;
+			v[2] = 0;
+			if(monitor->cylinder_depth)
 			{
-				rz = (1.0f-yf)/aspect*sin_ksv+z*cos_ksv;
-				yf = 1.0f-((1.0f-yf)*cos_ksv-z*aspect*sin_ksv);
-				z = rz;
+				v[2] = (1.0f-cos(v[0]*cyl_arc))*cyl_radius-monitor->cylinder_depth;
+				v[0] = sin(v[0]*cyl_arc)*cyl_radius;
 			}
-			else if(monitor->keystone_vertical<0)
-			{
-				rz = z*cos_ksv-yf/aspect*sin_ksv;
-				yf = yf*cos_ksv+z*aspect*sin_ksv;
-				z = rz;
-			}
-			scale = monitor->perspective/(monitor->perspective+z);
-			v[0] = 0.5f+(xf-0.5f)*scale;
-			v[1] = monitor->vertical_center+(yf-monitor->vertical_center)*scale;
 		}
+
+	for(y=t; y<=t; --y)
+		for(x=t; x<=t; --x)
+		{
+			float *v;
+			float px, py, pz;
+			float scale;
+
+			v = vertex_data+(y*(t+1)+x)*3;
+			px = v[0]-eye[0];
+			py = (v[0]-eye[0])*look[0] - (v[1]-eye[1])*look[2] + (v[2]-eye[2])*look[1];
+			pz = (v[0]-eye[0])*look[0] + (v[1]-eye[1])*look[1] + (v[2]-eye[2])*look[2];
+			scale = monitor->perspective/pz;
+
+			v = vertex_data+(y*(t+1)+x)*4;
+			v[0] = px*scale+0.5f;
+			v[1] = py*aspect*scale+monitor->vertical_center;
+			v[2] = (monitor->x+(float)x*monitor->width/t)/screen->width;
+			v[3] = 1.0f-(monitor->y+(1.0f-(float)y/t)*monitor->height)/screen->height;
+		}
+
 	glBindBuffer(GL_ARRAY_BUFFER, monitor->vertex_buffer);
 	glBufferData(GL_ARRAY_BUFFER, data_size, vertex_data, GL_STATIC_DRAW);
 	glBindBuffer(GL_ARRAY_BUFFER, 0);