The situations that I have determined in your project are as follows: 1) The dimensions of the object you use as a land element are excessively large. Since ideCAD's new rendering engine works on a physical basis, the use of such large (land) and small-sized (structure) elements together causes disproportionateness in light calculations and slows down the rendering. In addition, erroneous results can be obtained as an image. An area of approximately 500x500m will do your job for this render. This is the primary reason for the slow rendering in this project. (When you shrink the land, 640x480 rendering takes about 3 minutes). 2) Max. reflection 3 is left. This is a level that is rarely required (it is used to see an object by reflecting like a mirror from 3 surfaces.) In a typical architectural project, max. You rarely need to set reflection more than 1. This is a factor that will slow down the render. 3) You left the gamma setting at 1.1, the standard gamma setting should be 2.2. Depending on the effect, this setting can be played in the range of 2-2.4, but a setting like 1.1 will still give an unrealistic result. 4) I think you tried the user-defined settings to find the reason for the slowness, but the settings like 1 photon count are a bit ridiculous. For typical daylight outdoor rendering, the medium quality setting will do 90% of your work with no adjustments. You can get the final render on high or at the highest setting, but it won't make much difference with the medium setting, especially for outdoor rendering.