Immediate vs retained modeĪnother important trend in the recent evolution of OpenGL consists in the elimination of the immediate mode calls ( glBegin/ glVertex/ glEnd) from the API, in favor of the use of Vertex Buffer Objects (VBOs). A significant advantage of moving to programable pipelines across all platforms is the increased performance, since GLSL shaders can be exactly customized to the kind of rendering Processing does. Fortunately, most GPUs released over the past 3-4 years do support programmable pipelines, including the integrated chipsets from Intel. Likewise, P3D on the desktop will also fail to run if the video card doesn’t not properly support OpenGL 2.0 and programmable shaders. Froyo (2.2) still makes up for a significant proportion of the devices currently in use (around 25% according to the latest stats from Google) but unfortunately its GLES2 Java bindings are broken, which lead us to define 2.3 as the minimum requirement for OpenGL on Android. However, there is an important practical consequence of upgrading P3D to a fully programmable pipeline: on the Android side, devices that don’t support GLES2 won’t be able to run P3D sketches, this effectively excludes any Android smartphone or tablet which is not running Gingerbread (Android 2.3) or newer. Following this trend, the new P3D renderer in Processing implements all the drawing operations with GLSL shaders, both on desktop (PC/Mac) and Android. From the perspective of most users, this change won’t be very noticeable, since the new P3D shaders are meant to reproduce as closely as possible the visual output of the older software-based P3D and OPENGL renderers in Processing 1.x. OpenGL ES 2.0 (GLES2) on mobile devices as well as WebGL ditched the fixed functionality entirely so that drawing any kind of 3D scene on mobile or web requires writing the appropriate GLSL shaders. GPUs and graphics APIs like OpenGL have been moving away from the fixed-pipeline model to a fully programmable approach where every rendering operation needs to be coded as a shader program.
Update: With the release of Processing 2.0 final, some of the contents in this post are outdated, please check the new reference, and tutorials – specially those about P3D, PShape and shaders – for a detailed description of the finalized API. I will describe some important elements of P3D in this post. A major update in alpha 5 is the inclusion of the new OpenGL renderer for the desktop and Android modes, called P3D, which has been rewritten from the ground up in order to offer improved performance. The march towards the 2.0 version of Processing reached an important milestone with the alpha 5 release, available for download since last Friday. The detailed list of changes is here, while the wiki offers a more in-depth discussion of the new features and ongoing changes.
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