get projection image without rendering to screen

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Volkan
Volkan 2011-6-3
回答： George Abrahams 2024-2-10
Hi,
I have an 3d model and ı want to take its 2d projection.
I can get it from rendered projection from figure with the method below succesfully.
trimesh(...
tl, shp(:, 1), shp(:, 3), shp(:, 2), ...
'EdgeColor', 'none', ...
'FaceVertexCData', tex/255, 'FaceColor', 'interp', ...
'FaceLighting', 'phong' ...
set(gca, ...
'DataAspectRatio', [ 1 1 1 ], ...
'PlotBoxAspectRatio', [ 1 1 1 ], ...
'Units', 'pixels', ...
'GridLineStyle', 'none', ...
'Position', [ 0 0 fig_pos(3) fig_pos(4) ], ...
'Visible', 'off', 'box', 'off', ...
'Projection', 'perspective' ...
);
h=gca;
F=getframe(h);
im=F.cdata;
Now, I wanna take projection image without the need of rendered to screen. Because ı used the method on an optimization process and rendering process costs so much to me.
Thanks for your time.

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采纳的回答

Jonas Reber
Jonas Reber 2011-6-3
you could calculate the perspective projection of your model yourself as you have all the information on camera position, look at point, etc. this ends up to a matrix multiplication (see Shirleys "Fundamentals of Computer Graphics" or Wikipedia: http://en.wikipedia.org/wiki/3D_projection#Perspective_projection)
but what you probably are looking for is the matlab function "viewmtx" (<http://www.mathworks.com/help/techdoc/ref/viewmtx.html)>?
  2 个评论
Volkan
Volkan 2011-6-6
Thank you Jonas,
I projected the point succesfully with the method you proposed. I used viewmtx function.
In the code which I wrote on my question, the texture data has rendered with trimesh function.
Now i projected the points on 2d space but i dont know how can i brush the area between points.(using my texture data). I have rgb color values for every vertex.
Thank you again for your support.
Jonas Reber
Jonas Reber 2011-6-7
Hi Volkan,
once you have your 2D points you can use patch (http://www.mathworks.com/help/techdoc/ref/patch.html) to draw things.
Take a look at the explanation given in the documentation - it is quite good. (i.e. you need to set the 'FaceVertexCData')

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更多回答（1 个）

George Abrahams
George Abrahams 2024-2-10
My 3D Rendering Toolbox on File Exchange is one option for doing this. The world2image function performs the perspective projection you've calculated yourself, and a bit more.
If you're okay with 2D vector graphics (composed of polygons), i.e., you don't need a rastered image (composed of pixels), that right there is enough. Otherwise, the projection is only the first step, as you've discovered.
My toolbox also contains a rasterize function. However, given that you need interpolated face colors (from vertex colors) and face lighting, Patch Software Render or Rendering Pipeline may suit better, although I have no experience with them.

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