With the innovation and integration of media objects in multimedia applications, the importance of architectural support for different types of media objects, e.g., image, video and graphics, in one platform has significantly increased. While several approaches based on vector or VLIW architectures, e.g., Vector-IRAM and Imagine, have been pursued, they are not as effective as dedicated graphics pipelines for high-performance 3D graphics. We have explored a new programmable computing architecture based on a 3D graphics pipeline, which utilizes dedicated hardware resources in the 3D graphics pipeline for other types of multimedia computing. Adding programmable flexibility to a graphics pipeline for texture mapping has proven to be effective, e.g., Pixel Shader. However, due to the diversity of imaging and video processing applications, there are several challenges associated with converting a fixed graphics pipeline to a flexible multimedia computing engine. In this paper, we identify the additional architectural requirements, introduce the proposed architecture with extension details, and present the results of the performance evaluation. With cycle-accurate simulation of several benchmark functions, we have verified that the proposed architecture outperforms a modern powerful mediaprocessor in imaging and video processing by a factor of 1.3 to 7.5. The 3D graphics performance would not change much because the additional pipeline stages for the extension result in longer pipeline latency but similar throughout.