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  #1  
Old 03-07-2013, 09:10 AM
hzhao hzhao is offline
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Join Date: Sep 2012
Posts: 16
object on the fly--how to change color of particular vertex

With the following code, I created an object on-the-fly, a green polygon. Then I want to create a vertical transparent stripe, that is, set vertex 2 and 5 to be transparent. But the code doesn't work this way. Why? Thanks!

viz.startLayer(viz.POLYGON)
viz.vertexColor(viz.GREEN)

viz.vertex(0.0,0.0,0.0)
viz.vertex(0.5,0.0,0.0)
viz.vertex(0.6,0.0,0.0)
viz.vertex(1.0,0.0,0.0)
viz.vertex(1.0,1.0,0.0)
viz.vertex(0.6,1.0,0.0)
viz.vertex(0.5,1.0,0.0)
viz.vertex(0.0,1.0,0.0)
target=viz.endLayer()

target.dynamic()

target.setVertexColor(2,[0,0,1,0.2])
target.setVertexColor(5,[0,0,1,0.2])
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  #2  
Old 03-07-2013, 12:36 PM
hzhao hzhao is offline
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Join Date: Sep 2012
Posts: 16
What I want to do is to vary transparency within an object. How to do that ?
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  #3  
Old 03-20-2013, 08:42 AM
farshizzo farshizzo is offline
WorldViz Team Member
 
Join Date: Mar 2003
Posts: 2,849
Many OpenGL drivers will internally break up POLYGON shapes into triangles. Try using QUADS instead.
Code:
viz.startLayer(viz.QUADS)
viz.vertexColor(viz.GREEN)
viz.vertex(0.0,0.0,0.0)
viz.vertex(0.5,0.0,0.0)
viz.vertex(0.5,1.0,0.0)
viz.vertex(0.0,1.0,0.0)

viz.vertex(0.5,0.0,0.0)
viz.vertex(0.6,0.0,0.0)
viz.vertex(0.6,1.0,0.0)
viz.vertex(0.5,1.0,0.0)

viz.vertex(0.6,0.0,0.0)
viz.vertex(1.0,0.0,0.0)
viz.vertex(1.0,1.0,0.0)
viz.vertex(0.6,1.0,0.0)
target=viz.endLayer()

target.dynamic()

target.setVertexColor(5,[0,0,1,0.2])
target.setVertexColor(6,[0,0,1,0.2])
target.setVertexColor(8,[0,0,1,0.2])
target.setVertexColor(11,[0,0,1,0.2])
Depending on your needs, you might be able to just use an alpha texture on a single quad to achieve the transparency.
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