OpenGL ES 1.1 is a de facto standard for the 3D graphics API on embedded systems and handheld devices including mobile phones. We present design process and implementation results of our software OpenGL ES 1.1 product. Since the standard document only specifies the API functions and their external actions, the implementer should design all the details of the internal 3D graphics pipeline and exhaustively optimize them. To clearly express the internal pipeline and to explicitly represent related state variables, we introduce some enhancements to UML activity diagrams. Based on these enhanced diagrams, we accomplished the initial draft design and iterative optimizations of the internal pipeline. During the implementation stage, starting from our previous wrapper implementation, we used an iterative block-by-block implementation scheme with immediate verifications. Finally, we achieved a full software implementation of OpenGL ES 1.1, which passes all the official conformance test suites and also satisfies all the requirements in the standard specification. This product is now ready for commercial services.