hi Andre…
i believe that, in order to improve, we have to follow some process…
as i understand, a good render is something like this…
modelling (30%)
illumination (30%)
materials (20%)
post production (20%)
so, first thing i would do, is finish the model, then you have to work with your illumination. for that check the tutorial. if you’re using phisical camera, then you have to make lots of tests till you get the right mood. the same thing goes for materials, but in this particular case, i believe that you will improve this renders a lot if you add some texture layers to the grass in photoshop. you also need some color corrections. grass is way too bright, at least for me. all the trees look exactly the same. you could also scale and rotate them…
it’s a large sceene, so it’s complicated to handle, therefore, this is a good job, but there’s still a lot to improve.
try using an HDRI for the illumination. i think it’ll look more real.
great start
4 the water to look more real, try using sky backgrounds, reflections will improve the scene. u can use grass displacement and also some border details maybe.
in landscape architecture, I think that u can try different softwares, 3dmax and maya have great landscape plugins like autograss, xfrog, vue… sketchup is not so good in handling high polygon trees & …hope that one day it will improve in this field.
