programming blend function

最新推荐文章于 2024-10-10 08:55:43 发布

原创最新推荐文章于 2024-10-10 08:55:43 发布 · 570 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#blend #function #shader #textures #primitive #input

讨论了使用着色器进行RGBE编码（HDRI）的两个片段的混合过程。由于OpenGL的glBlendFunc仅适用于固定管线，更复杂的功能需通过自定义着色器实现。未来OpenGL3将移除固定管线，所有操作将由用户自行定义。

导读：
　　Antonio Bleile
　　 programming blend function
　　Hi,
　　I'm currently trying to blend two RGBE (HDRI encoded) fragments
　　together.
　　The only way this seems to work is through shaders (the shader takes
　　as
　　input a copy of the RGBE encoded framebuffer, the shader then blends
　　the fragments togehter). There is no way to "customize/program" the
　　glBlendFunc,
　　right? What about OpenGL 3? Will that allow it? And there's absolutely
　　no way
　　for the fragment shader to access the framebuffer, right? What about
　　FBO's?
　　Those are ordinary textures, what happens if I just give a fragment
　　shader the
　　current FBO render target as input (sounds insane, but it might be
　　legal?).
　　Thank you &Regards,
　　Toni
　　
　　09-16-2007, 03:33 PM
　　Wolfgang Draxinger
　　 Re: programming blend function
　　Antonio Bleile wrote:
　　>Hi,
　　>
　　>I'm currently trying to blend two RGBE (HDRI encoded)
　　>fragments together.
　　>The only way this seems to work is through shaders (the shader
　　>takes as input a copy of the RGBE encoded framebuffer, the
　　>shader then blends the fragments togehter).
　　>There is no way to "customize/program" the glBlendFunc, right?
　　glBlendFunc controls a part of the fixed function pipeline.
　　Anything different from the fixed function pipeline must be done
　　with shaders.
　　>What about OpenGL 3? Will that allow it?
　　OpenGL 3 will discard the fixed function pipeline completely,
　　i.e. you must define all vertex and framgment processing
　　yourself. This will also mean, that a lot of API functions will
　　be removed, among them glBlendFunc.
　　>And there's absolutely no way for the fragment shader to access
　　>the framebuffer, right?
　　No, since the framebuffer is in constant change while a primitive
　　is processed. So there must be a copy taken somewhere in the
　　process.
　　>What about FBO's? Those are ordinary textures,
　　No they aren't. A FBO can be used as texture, but can do also
　　other stuff.
　　>what happens if I just give a fragment shader the current FBO
　　>render target as input (sounds insane, but it might be legal?).
　　Read the FBO spec, it contains an own paragraph exactly about
　　this. You can't bind a FBO that's a render target as texture
　　within the same render context. And you can't make a texture
　　bound FBO as render target.
　　Wolfgang Draxinger
　　--
　　E-Mail address works, Jabber: hexarith--at--jabber.org, ICQ: 134682867
　　
　　09-16-2007, 10:16 PM
　　fungus
　　 Re: programming blend function
　　On Sep 16, 4:42 pm, Antonio Bleile wrote:
　　>There is no way to "customize/program" the
　　>glBlendFunc, right?
　　Right.
　　>What about OpenGL 3? Will that allow it?
　　No. At the hardware level there's a big gap
　　between the pixel shading operations and
　　the blending operations. Bringing them
　　together would kill performance.
　　--
　　
　　/ O O /
　　/_____/ FTB. Remove my socks for email address.
　　
　　09-17-2007, 02:58 AM
　　Antonio Bleile
　　 Re: programming blend function
　　On Sep 17, 5:16 am, fungus wrote:
　　>On Sep 16, 4:42 pm, Antonio Bleile wrote:
　　>
　　>>There is no way to "customize/program" the
　　>>glBlendFunc, right?
　　>
　　>Right.
　　>
　　>>What about OpenGL 3? Will that allow it?
　　>
　　>No. At the hardware level there's a big gap
　　>between the pixel shading operations and
　　>the blending operations. Bringing them
　　>together would kill performance.
　　Alright.....
　　Thank you guys!
　　Toni

本文转自
http://objectmix.com/graphics/136729-programming-blend-function.html