Functions to adjust the coordinate frame

mglVisualAngleCoordinates: Visual angle coordinates

purpose: Sets view transformation to correspond to visual angles (in degrees) given size and distance of display. Display must be open and have valid width and height (defined in MGL variable)
usage: mglVisualAngleCoordinates(physicalDistance,physicalSize);

argument value
physicalDistance [distance] in cm
physicalSize [width height] in cm
mglOpen
mglVisualAngleCoordinates(57,[16 12]);

mglScreenCoordinates: Pixel coordinate frame

purpose: Set coordinate frame so that it is in pixels with 0,0 in the top left hand corrner
usage: mglScreenCoordinates()

mglTransform: Low-level function to adjust transforms

purpose: applies view transformations
usage: mglTransform(whichMatrix, whichTransform, [whichParameters])

argument value
whichMatrix 'GL_MODELVIEW', 'GL_PROJECTION', or 'GL_TEXTURE'
whichTransform 'glRotate', 'glTranslate', 'glScale','glMultMatrix', 'glFrustum', 'glOrtho','glLoadMatrix', 'glLoadIdentity', 'glPushMatrix','glPopMatrix', 'glDepthRange', or 'glViewport'
whichParameters function-specific; see OpenGL documentation

You can also specifiy one of GL_MODELVIEW, GL_PROJECTION, or GL_TEXTURE and a return variable current matrix values. If two outputs are specified, the result of the computation will be returned.

This function is usually not called directly, but called by mglVisualAngleCoordinates or mglScreenCoordinates to set the transforms

mglHFlip: Horizontally flip coordinates

purpose: flips coordinate frame horizontally, useful for when the display is viewed through a mirror
usage: mglHFlip()

mglOpen
mglVisualAngleCoordinates(57,[16 12]);
mglHFlip
mglTextSet('Helvetica',32,1,0,0,0,0,0,0,0);
mglTextDraw('Mirror reversed',[0 0]);
mglFlush;

mglVFlip: Vertically flip coordinates

purpose: flips coordinate frame vertically
usage: mglVFlip

mglOpen
mglVisualAngleCoordinates(57,[16 12]);
mglVFlip
mglTextSet('Helvetica',32,[1 1 1],0,0,0,0,0,0,0);
mglTextDraw('Vertically flipped',[0 0]);
mglFlush;
software/mgl/functionreferencecoordinateframes.txt · Last modified: 2009/05/01 13:32 (external edit)
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