Doris

hierarchy.lua

This is an example of using the OpenGL matrix stack to render a linked hierarchy of objects. When the rotators are manipulated the boxes, and their children spin. All of the boxes can be moved arond using the translator as well.

Screenshot

hierarchy.lua screenshot

Source Code


 -- Simple hierarchy example
 -- $Id: hierarchy.lua,v 1.5 2002/06/24 07:06:31 trout Exp $
-- Create a hierarchy node. A table is passed containing information
 -- about the position, size and children of the node.
 function makeNode(t)
    t.pos = Matrix:new() -- positioning matrix
    local p = t.vpos
    t.pos:makeTranslate(p[1],p[2],p[3])
    t.rot = Matrix:new() -- rotation matrix
    return t
 end
-- Create some nodes to draw and manipulate.
 n4 = makeNode{vpos={0.5,0.5,0.5}, size=0.5}
 n3 = makeNode{vpos={1,1,1}, kids={n4}, size=1}
 n2 = makeNode{vpos={2,2,2}, kids={n3}, size=2}
 n1 = makeNode{vpos={-2,-2,-2}, size=1}
 n0 = makeNode{vpos={0,0,0}, kids={n1,n2}, size=4}
-- Put the nodes in a list for ease of use
 nodes = {n0,n1,n2,n3,n4}
-- Render a given node and then its children
 function RenderNode(n)
    glPushMatrix() -- jump into new frame
      glMultMatrix(n.pos) -- position ourselves
      glMultMatrix(n.rot) -- rotate ourselves
      --glutWireCube(n.size)
      glutSolidCube(n.size)
      for _,k in (n.kids or {}) do
        RenderNode(k)
      end
    glPopMatrix()
 end
-- The scene render callback function.
 function RenderScene()
   if not first then
      first = 1
      glEnable(GL_LIGHTING)
      glEnable(GL_LIGHT0)
      glLight(GL_LIGHT0, GL_POSITION, {10,10,10})
      glLight(GL_LIGHT0, GL_AMBIENT, {.3,.3,.3})
      glLight(GL_LIGHT0, GL_DIFFUSE, {.7,.2,0})
      glClearColor(.9,.9,.9,1.0)
    end
   
    glClear(GL_DEPTH_BUFFER_BIT + GL_COLOR_BUFFER_BIT)
    gluLookAt(0,0,15, 0,0,0, 0,1,0)
    glMatrixMode(GL_MODELVIEW)
    glLoadIdentity()
    RenderNode(n0) -- start rendering our nodes from the root
 end
-- Create the main window
 wmain = Window:create{
      title="Doris: Simple hierarchy example",
      render=RenderScene
 }
-- Add a window at the bottom
 sw=SubWindow{ parent=wmain, side="bottom" }
-- Create a rotator for each node which will rotate it
 for i=1,getn(nodes) do
      local n = nodes[i]
      Rotator{ parent=sw, text="Rotate node "..i,
             value=n.rot, -- matrix to manipulate
              line="|", -- draw line seperator
              spin=.97 -- allow it to spin with a little damping
      }
 end
-- Create translator for left and right movement (in xy)
 Translator{ parent=sw, type="xy", text="Move cubes", space="v",
      update = function(p)
        local v = n0.vpos
        v[1],v[2] = p[1]*.1, p[2]*.1
        n0.pos:makeTranslate(v[1],v[2],v[3])
      end
 }
-- Move back and forth (in z)
 Translator{ parent=sw, type="z", line="v", text="Move cubes",
      update = function(p)
        local v = n0.vpos
        v[3] = p*.1
        n0.pos:makeTranslate(v[1],v[2],v[3])
      end
 }
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