Please recommend PC Specs For CAD & 3ds max especially for Vray Rendering?

intel pentium 7th gen processors16 to 32 gb memory HDD 1 or  2 TBSDD 100 gbnvidia geforce 1080 GTX with 4 ti 8 GB 

Since you want the best possible for 3d work I suggest the Quadro k4000 if u will be working with large scene or high poly objects, particles, etc.

The k4000 will give you far better viewport performance than gtx 780. An alternative to quadro k4000 is the Firepro w7000 if CUDA or GPU rendering is not important to you.

However, you can go for the gtx 780 if your work is not heavy, also it will give you better GPU rendering performance than the k4000 due to higher clock and more CUDA cores, but dont leave it rendering for long hours, gtx is not built with stability in mind.While 32Gbs of RAM is a bit overkill for 3D modeling, but if you will be doing video editing that will help, otherwise go for 16Gbs.

CAD & 3ds max One of the best tools in this area

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l agree with mr.Khaled thanks for invitation

System Requirements for Autodesk Inventor 2017 Windows Operating System ¹

• Microsoft® Windows® 10 (desktop OS)
• 64-bit Microsoft Windows 8.1 with Update KB2919355
• 64-bit Microsoft Windows 7 SP1

CPU Type ² Recommended:Intel® Xeon® E3 or Core i7 or equivalent, 3.0 GHz or greaterMinimum:64-bit Intel or AMD, 2 GHz or faster Memory ³ Recommended:20 GB RAM or moreMinimum:8 GB RAM for less than 500 part assemblies Disk Space Installer plus full installation: 40 GB Graphics Recommended:Microsoft Direct3D 11® or capable graphics card or higherMinimum:Microsoft Direct3D 10® capable graphics card or higherSee the Certified Hardware Display Resolution 1280 x 1024 or higher.Recommended scaling: 100%, 125%, 150% or 200%. Other

• DVD-ROM ⁴
• Internet connection for Autodesk® 360 functionality, web downloads, and Subscription Aware access
• Adobe® Flash® Player 15 ⁵
• Microsoft Internet Explorer® 11 or equivalent
• Full local install of Microsoft® Excel 2010, 2013 or 2016 for iFeatures, iParts, iAssemblies, thread related commands, clearance/threaded hole creation, Global BOM, Parts Lists, Revision Tables, spreadsheet-driven designs and Studio animation of Positional Representations. Excel Starter®, Online Office 365® and OpenOffice® are not supported.
• 64-bit Microsoft Office is required to export Access 2007, dBase IV, Text and CSV formats.
• Microsoft .NET Framework 4.6 or later
• Virtualization supported on Citrix® XenApp™ 7.7 and 7.8; Citrix XenDesktop™ 7.7 and 7.8 (requires Inventor Network Licensing).