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Here's what I've managed to work out so far - as you can see, it yields a
view-frustum-shaped frame, but it seems I somehow have the aspect ratio wrong,
and the [real] camera is WAY back from where the placeholder scene camera is.
Not sure where my errors lie.
Perhaps someone could take a look at my values, assumptions, and math.
Also, I peeked at the source code, and it looked to me like the default camera
angle is 90. The docs imply 67.380
I'd like to get this worked out so I can start playing with frustum culling - it
seems that would be a powerful tool for large scenes with lots of objects.
See:
http://www.flipcode.com/archives/Frustum_Culling.shtml
--------------------------------------------------------------
#version 3.7;
global_settings {
assumed_gamma 1.0
}
//------------------------------------------
// sets up a model scene and views from an alternate viewpoint
//
// POV-Ray Scene SDL written by
// Bill Walker - 2016
//------------------------------------------
#include "colors.inc"
#include "debug.inc"
Set_Debug (true)
#include "math.inc"
#include "metals.inc"
#include "stones1.inc"
#include "textures.inc"
#include "woods.inc"
#declare Camera_Origin = camera {
location <0, 0, 0>
right x*image_width/image_height
look_at <0, 0, 0.01>}
#declare Camera_Angle = camera {
location <0.0 , 0.0, -100.0>
right x*image_width/image_height
look_at <100, 30, 0>}
#declare Camera_Front = camera {
location <0.0, 0, -70.0>
//location <0.0, 12, -10.0>
right x*image_width/image_height
look_at <0, 0, 0>}
#declare Camera_Rear = camera {
location <0.0, -100.0, -300.0>
right x*image_width/image_height
look_at <0, 0, 0>}
#declare Camera_Top = camera {
location <0, 25.0, 0>
right x*image_width/image_height
look_at <0, 0, 0>}
#declare Camera_Iso = camera {
location <-50, 0, 0>
right x*image_width/image_height
look_at <0, 0, 0>}
//####################
camera {Camera_Front }
//####################
light_source{ <50, 50, -100> color rgb <1, 1, 1>} // White top
//light_source{ <0, 0, -100> color rgb <1, 1, 1>} // White Front
sky_sphere {
pigment {
gradient <0, 1, 0>
color_map {
[0 color rgb <1, 1, 1> ]
[0.4 color rgb <0, 0, 0.8> ]
[0.6 color rgb <0, 0.14, 0.8> ]
[1.0 color rgb <1, 1, 1> ]
}
scale 2
}
}
/*
CAMERA TYPE: perspective
angle : ~67.380 ( direction_length=0.5*
right_length/tan(angle/2) )
confidence : 0.9 (90%)
direction : <0,0,1>
focal_point: <0,0,0>
location : <0,0,0>
look_at : z
right : 1.33*x
sky : <0,1,0>
up : y
variance : 1/128
direction_length = 0.5 * right_length / tan(angle / 2)
*/
#declare Camera_Location = <0, 0, 0>;
#declare P = Camera_Location;
#declare Camera_LookAt = <0, 0, 30>;
#declare ResolutionX = image_width;
#declare ResolutionY = image_height;
#declare Distance = Camera_LookAt - Camera_Location;
#declare V = vnormalize(Distance);
#declare Up = <0, 1, 0>;
#declare Right = <ResolutionX/ResolutionY, 0, 0>;
//#declare Right = vcross(V, Up);
#declare W = Right;
#declare nDis = 10;
#declare fDis = 30;
// Field of View (fov)
#declare Fov = 67.380;
#declare AR = ResolutionX/ResolutionY;
#declare Hnear = 2*tan(Fov/2)*nDis;
#declare Wnear = Hnear * AR;
#declare Hfar = 2*tan(Fov/2)*fDis;
#declare Wfar = Hfar * AR;
#declare Cnear = P + V * nDis;
#declare Cfar = P + V * fDis;
#declare NearTopLeft = Cnear + (Up * (Hnear/2)) - (W * (Wnear/2));
#declare NearTopRight = Cnear + (Up * (Hnear/2)) + (W * (Wnear/2));
#declare NearBottomLeft = Cnear - (Up * (Hnear/2)) - (W * (Wnear/2));
#declare NearBottomRight = Cnear - (Up * (Hnear/2)) + (W * (Wnear/2));
#declare FarTopLeft = Cfar + (Up * ( Hfar/2)) - (W * ( Wfar/2));
#declare FarTopRight = Cfar + (Up * ( Hfar/2)) + (W * ( Wfar/2));
#declare FarBottomLeft = Cfar - (Up * ( Hfar/2)) - (W * ( Wfar/2));
#declare FarBottomRight = Cfar - (Up * ( Hfar/2)) + (W * ( Wfar/2));
//#declare Towards = Distance / abs(Camera_Location.z);
// direction_length = 0.5 * right_length / tan(angle / 2)
// tan(angle / 2) * direction_length = 0.5 * right_length
// tan(angle / 2) = (0.5 * right_length) / direction_length
// (angle / 2) = atan2( (0.5 * right_length), direction_length)
// angle = 2* atan2( (0.5 * right_length), direction_length)
// tan (Theta) = Opposite / Adjacent
// tan (Theta) = (ResolutionX/2) / Distance
// Distance * tan (Theta) = (ResolutionX/2)
// 2 * Distance * tan (Theta) = ResolutionX
// Theta = atan2 ((ResolutionX/2), Distance)
//#declare Angle = atan2 ((ResolutionX/2), Distance);
//#declare Angle = 67.38;
//#declare Distance = 0.5 * Right / tan(radians(Angle) / 2);
//#declare Top_Left = Camera_Location + (Distance * Towards * <0, 0, 1>) -
(Distance * tan(Angle) * Right);
//#declare Top_Right = Camera_Location + (Distance * Towards * <0, 0, 1>) +
(Distance * tan(Angle) * Right);
// {Be sure to include debug.inc file!}
#debug concat( "Distance = ", vstr(3, Distance, ", ", 3, 3), " \n")
#debug concat( "Right = ", vstr(3, Right, ", ", 3, 3), " \n")
//#debug concat( "Top_Left = ", vstr(3, Top_Left, ", ", 3, 0), " \n")
//#debug concat( "Top_Right = ", vstr(3, Top_Right, ", ", 3, 0), " \n")
sphere {Camera_Location, 0.1 pigment {Green}}
sphere {Camera_LookAt, 0.5 pigment {Yellow}}
//sphere {Top_Left, 0.2 pigment {Red}}
//sphere {Top_Right, 0.2 pigment {Red}}
//cylinder {Top_Left, Top_Right, 0.05 pigment {Blue}}
#declare NearSphere = 0.2;
#declare FarSphere = 0.2;
sphere {NearTopLeft, NearSphere pigment {Orange}}
sphere {NearTopRight, NearSphere pigment {Orange}}
sphere {NearBottomLeft, NearSphere pigment {Orange}}
sphere {NearBottomRight, NearSphere pigment {Orange}}
cylinder {NearTopLeft, NearTopRight, NearSphere/2 pigment {Orange}}
cylinder {NearTopRight, NearBottomRight, NearSphere/2 pigment {Orange}}
cylinder {NearBottomRight, NearBottomLeft, NearSphere/2 pigment {Orange}}
cylinder {NearBottomLeft, NearTopLeft, NearSphere/2 pigment {Orange}}
sphere {FarTopLeft, FarSphere pigment {Violet}}
sphere {FarTopRight, FarSphere pigment {Violet}}
sphere {FarBottomLeft, FarSphere pigment {Violet}}
sphere {FarBottomRight, FarSphere pigment {Violet}}
cylinder {FarTopLeft, FarTopRight, FarSphere/2 pigment {Violet}}
cylinder {FarTopRight, FarBottomRight, FarSphere/2 pigment {Violet}}
cylinder {FarBottomRight, FarBottomLeft, FarSphere/2 pigment {Violet}}
cylinder {FarBottomLeft, FarTopLeft, FarSphere/2 pigment {Violet}}
cylinder {Camera_Location, FarTopRight, NearSphere/2 pigment {White}}
cylinder {Camera_Location, FarBottomRight, NearSphere/2 pigment {White}}
cylinder {Camera_Location, FarBottomLeft, NearSphere/2 pigment {White}}
cylinder {Camera_Location, FarTopLeft, NearSphere/2 pigment {White}}
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