Wide-angle view

[Brett Lindberg]

Is there a smooth way in Vizard to generate a wide view FOV (say, greater than 180 degrees?)

I'm trying to "unwrap" a spherical panoramic view into a quad, but I can't get it right: if I set FOV greater than 90, it messes everything up. I've tried to get around this by compositing four 90-degree views, but there is significant distortion at the boundaries.

What I'd like is a wide, short view (say 4:1, across the top of the window), rendering the a 360 panorama of same scene as the normal main view.

[Jeff]

Have you gotten any further with this? I'll check with our dev team to see if they have some suggestions.

[Brett Lindberg]

Haven't gotten it to work yet: trying to make a bunch of very narrow views stuck close together, but this isn't that great a solution, because I want to be able to get coordinates.

[farshizzo]

You need to render multiple views to a texture and then render the textures to the screen using either an undistortion mesh or shader. There should be examples on the forum for rendering views to a texture.

[Brett Lindberg]

I hacked my way around and came up with this: draws 40 windows across the top of the window. I could render to texture, and make one window, but would that be a lot better?

import viz
import math

class PanoWindowGroup:
def __init__(self, SubWins=40, windowHeight=0.3, vertFOV=90):


self.numSubWins = SubWins

self.winHeight = windowHeight

self.winFOV = 360.0/self.numSubWins

self.vFOV=vertFOV
self.sizeRat = 1.0/self.numSubWins

self.size = (self.sizeRat, self.winHeight)

self.subWinArr = []

#experimentally derived sub-window FOV ratio:
# self.subWinFOVrat = 4.3015/(pow(self.numSubWins,1.113))

for i in range(self.numSubWins):
scrPos = ((i*self.sizeRat),1.0)
direction = i*self.winFOV-60.0
print "Direction= ", direction
subWin = PanoSubWindow(scrPos, self.size, direction, self.winFOV, self.vFOV, self.subWinFOVrat )
self.subWinArr.append(subWin)


class PanoSubWindow:


def __init__(self, scrPos, sizer, direction, winFOV, vFOV, sWFR, viewPos=[0,0,0]):
print "Inputs: ", "scrPos= ", scrPos, " sizer= ", sizer, "direction= ",direction, "winFOV= ", winFOV, "vFOV= ", vFOV
self.vFOV = vFOV
self.size = sizer
self.subwindow = viz.addWindow(pos=scrPos, size=sizer)
self.subwindow.visible(0, viz.SCREEN)
self.subWinFOVrat = sWFR

self.subview = viz.addView()
self.subview.setPosition(viewPos)

self.subview.setEuler([direction,0,0])
self.subwindow.setView(self.subview)

# self.subwindow.fov(self.vFOV, self.subWinFOVrat)
self.subwindow.fov(self.vFOV, 0.075)

[Brett Lindberg]

Take 3: how do I render multiple views to one texture?
There's only one example on the forums: http://forum.worldviz.com/showthread.php?t=2003, but that's only for one view.

[farshizzo]

For each view, you would create a separate render node and render texture. You would then apply all the render textures from each view to a separate texture unit of a quad. Finally, you would apply a fragment shader on the quad that performs the undistortion using the different textures. I can provide some sample code that sets this up if you like, but you would still need to come up with your own shader code that performs the undistortion.

[Brett Lindberg]

A sample to get started would be great: the shader stuff should be doable.

[farshizzo]

Here is a sample script. The shader simply averages the image from each pass, you will need to replace that with your own shader code.import viz
viz.go()

FRAG = """
uniform sampler2D Pass1;
uniform sampler2D Pass2;
uniform sampler2D Pass3;
uniform sampler2D Pass4;

void main()
{
vec4 p1 = texture2D(Pass1, gl_TexCoord[0].xy);
vec4 p2 = texture2D(Pass2, gl_TexCoord[0].xy);
vec4 p3 = texture2D(Pass3, gl_TexCoord[0].xy);
vec4 p4 = texture2D(Pass4, gl_TexCoord[0].xy);

//TODO: Combine texture from each pass
gl_FragColor = (p1+p2+p3+p4) * 0.25;
}
"""

def CreateRenderPasses():

renderPass = []
uniforms = []

#Create post render pass that combines all passes
postRenderPass = viz.addRenderNode()
postRenderPass.setHUD(-1,1,-1,1,renderQuad=True)
postRenderPass.setOrder(viz.POST_RENDER,-1)

#Create each pass
for x in range(4):

#Create render texture
renderTexture = viz.addRenderTexture()

#Apply to post render pass
postRenderPass.texture(renderTexture,unit=x)

#Create uniform for texture unit
uniforms.append(viz.addUniformInt('Pass'+str(x+1), x))

#Create render node to render texture
renderNode = viz.addRenderNode()
renderNode.attachTexture(renderTexture)
renderPass.append(renderNode)

#Apply shader
shader = viz.addShader(frag=FRAG,uniforms=uniforms)
postRenderPass.apply(shader)

#Set rotation offset of each render pass
renderPass[0].setEuler(-30,0,0)
renderPass[1].setEuler(-10,0,0)
renderPass[2].setEuler(10,0,0)
renderPass[3].setEuler(30,0,0)

viz.add('gallery.ive')

CreateRenderPasses()