1. A computer-implemented method of graphics processing in a computer system that includes a processor and memory, the method comprising: receiving a parallel processing request at a parallel programming interface, the parallel processing request comprising an evaluation request of one or more parallel operations on one or more input arrays, wherein the parallel processing request is initially represented as a first expression tree, the first expression tree comprising two or more texture coordinate operations, wherein one or more nodes of the first expression tree comprise program objects that provide shader code corresponding to a graphics environment; with the computer system, composing the two or more texture coordinate operations to form a second expression tree having a composed texture read operation, wherein the composed texture read operation is a leaf of the second expression tree; with the computer system, creating one or more shader programs formed according to resource constraints of the graphics environment, wherein the shader programs comprise at least a portion of the shader code provided by one or more of the program objects; with the computer system, invoking the one or more shader programs in the graphics environment; receiving an output responsive to invoking the one or more shader programs in the graphics environment; and returning the output as a response to the evaluation request.