diff options
| -rw-r--r-- | 2d/transform.scm | 29 |
1 files changed, 28 insertions, 1 deletions
diff --git a/2d/transform.scm b/2d/transform.scm index e1dba7b..4edd080 100644 --- a/2d/transform.scm +++ b/2d/transform.scm @@ -25,6 +25,7 @@ #:use-module (srfi srfi-1) #:use-module (srfi srfi-9) #:use-module (srfi srfi-42) + #:use-module (2d math) #:use-module (2d vector2) #:export (make-transform make-transform* @@ -40,7 +41,8 @@ transform-translate transform-scale transform-rotate - orthographic-projection)) + orthographic-projection + perspective-projection)) (define-record-type <transform> (%make-transform matrix) @@ -183,3 +185,28 @@ FAR." (- (/ (+ top bottom) (- top bottom))) (- (/ (+ far near) (- far near))) 1)) + +(define (perspective-projection field-of-vision aspect-ratio near far) + "Return a new transform that represents a perspective projection +with a FIELD-OF-VISION in degrees, the desired ASPECT-RATIO, and the +depth clipping plane NEAR and FAR." + (let ((size (* near (tan (/ (degrees->radians field-of-vision) 2))))) + (let ((left (- size)) + (right size) + (top (/ size aspect-ratio)) + (bottom (/ (- size) aspect-ratio))) + (make-transform (/ (* 2 near) (- right left)) ;; First row + 0 + (/ (+ right left) (- right left)) + 0 + ;; Second row + 0 + (/ (* 2 near) (- top bottom)) + (/ (+ top bottom) (- top bottom)) + 0 + ;; Third row + 0 0 + (- (/ (+ far near) (- far near))) + (- (/ (* 2 far near) (- far near))) + ;; Fourth row + 0 0 -1 0)))) |