Sketchup renders(top/bottom): Sketchup, IRender nXt, Podium, Hypershot.Google Sketchup is one of the easier 3d modeling software packages out there to use with easy to load models from the web and single click application of materials. Where a lot of people feel a void comes in the final render. The program itself offers a variety of linear, sketchy options for final output but for that semi-realistic, shaded effect you really need to invest in a separate render engine. There are a wide variety of packages out there, most noted being Vray, but with this sophistication of a top notch renderer like Vray comes a semi-steep learning curve. There are a lot of sites out there dedicated to learning Vray, materials for Vray....invest some time to use this one, but if what you want is a fairly nice job of ambient light, shading, shadows without a lot of hassle, take a look at one of these three plugins for Sketchup:
Irender nXt
IRender allows quick setup for a nice looking render. Options for settings include usage of artificial light (with downloads for various lights off the web that automatically adjust to your scene or let you change the settings), natural light, override Sketchup sun settings, limited variables of materials (reflective quality of material, course or smooth setting for bump maps), adjustment of background colors for your render (or image as background), finished size of output option with a fairly quick render time. Where it might fall short for some is it's inability to handle alpha channel images well so trying to place a tree image (i.e. imagecel foliage) is next to impossible. A bonus to this render engine is it's recognition of Sketchup shadow settings in the render.
Podium
SU Podium for Sketchup is another fantastic photo-realistic renderer that is easy to operate and offers a variety of variables for you to set. The interface comes with a couple different settings and seems to react very nice in the Sketchup environment, materials can be adjusted for reflection and lighting attributes, great for outdoor architectural shots. Creating lights takes a little bit of patience but the final outcome is worth the effort. A bonus for it's ability to recognize alpha images so realistic looking people, trees, etc. that are masked can be interpreted. Preset lights can be downloaded form certain sites so Podium ranks very high in my book.
Hypershot
Hypershot is one of the best looking renders from the least amount of effort. This plugin opens in a new window allowing rich looking textures to be dragged and applied on screen, slower render time that IRender or Podium but very satisfying results that carry ambient occlusion similar to that you see from Vray. Excellent render for interior shots-I agree with Bunkspeed Hypershot's analysis of their product that touts "not like any typical or standard rendering software packages'-simple, fast and accurate. Only part that takes some getting used to is the camera adjustment but with simplistic adjustment of variables I find Hypershot to be a reliable asset for Sketchup.
