Multiscreen splicing can realize integral imaging light field 3D displays with various sizes; however, the 3D source generation process is complex. This study proposes a 3D source rendering platform that can provide sources for the multiscreen splicing realized integral imaging light field 3D display. The obtained 3D images can be reproduced accurately without misalignment. In the process of the 3D source rendering, first, the parameters such as the resolution of an elemental image array are calculated. The Open Graphics Library (OpenGL) is employed to render an initial elemental image array. Second, an elemental image array for the splicing realized integral imaging light field 3D display is obtained by splitting the initial elemental image array, using the projection transform, and splicing the sub-elemental image array. The 3D source rendering program is packaged as a visual 3D source rendering platform based on Qt (Application Development Framework), which supports the input of multiple formats of 3D models, such as .obj and .fbx, as well as the output of an elemental image array with resolution of 16K and above. The experimental results demonstrate that the elemental image array generated using the 3D source rendering platform can realize an accurate 3D image on an integral imaging light field 3D display that is spliced using dual 8K resolution screens. The proposed 3D source rendering platform can meet the 3D source generation needs of the multiscreen splicing realized integral imaging light field 3D display, which can be used during exhibitions and in other fields.