Add: common abbreviations

trees/ag-000N.tree

@@ -24,4 +24,5 @@
 \transclude{ag-000O}
 \transclude{ag-0018}
 \transclude{ag-0019}
+\transclude{ag-001G}
 }

trees/ag-0019.tree

@@ -14,7 +14,7 @@
 
 \card{example}{ray marching (naïve)}{
 
-\p{The following renders a scene with a unit sphere at the origin, the camera at #{(0,0,-8)} and looking at the origin, through a screen of height 1.0, centered at 5.0 from the camera.
+\p{The following renders a scene with a unit sphere at the origin, the camera at #{(0,0,8)} and looking at the origin, through a screen of height 1.0, centered at 5.0 from the camera.
 }
 
 \p{The color of pixels are adjusted so that they are brighter the closer they are to the camera, as if there is a light source at the camera. As it takes a fixed step size of 0.1 (not small enough), the sphere is not rendered smoothly, and clearly shows the stepping artifacts.
@@ -65,9 +65,9 @@ void mainImage(out vec4 pixelColor, in vec2 pixelCoordinate) {
 
     // set up camera and view ray
     float observerDistance = 8.0;
-    vec3 ro = vec3(0.0, 0.0, -observerDistance);
-    vec3 cameraBox = ro + vec3(uv, 5.0);
-    vec3 rd = normalize(cameraBox - ro);
+    vec3 ro = vec3(0.0, 0.0, observerDistance);
+    vec3 ta = ro - vec3(uv, 5.0);
+    vec3 rd = normalize(ta - ro);
 
     // ray march
     float t = rayMarch(ro, rd);

trees/ag-001G.tree

@@ -0,0 +1,28 @@
+\import{cg-macros}
+% clifford hopf spin tt ag math draft cg
+\tag{cg}
+
+% definition theorem lemma construction observation
+% convention corollary axiom example exercise proof
+% discussion remark notation
+% \taxon{}
+% \refcardt{lemma}{}{}{}{
+
+% kostecki2011introduction leinster2016basic nakahira2023diagrammatic rosiak2022sheaf
+
+% cox1997ideals gathmann2013commutative hart1996sphere gillespie2024ray winchenbach2024lipschitz
+
+\card{remark}{ }{
+\p{By convention, the GLSL community uses two-to-three letter variable names. Here are some common abbreviations:}
+
+\ul{
+\li{\code{ro} = ray origin}
+\li{\code{rd} = ray direction}
+\li{\code{ca} = camera}
+\li{\code{ta} = target (where the camera is pointing)}
+\li{\code{uv} = texture coordinates}
+}
+
+\p{Source: \link{https://raymarchingfundamentals.org/a-quick-background#the-raymarching-part}
+}
+}