Create More Believable Motion with Gen 4.5—Without Slowing Your Workflow
Gen 4.5 is Runway’s video generation model for text-to-video and image-to-video creation, announced on December 1, 2025 . Runway positions Gen 4.5 around state-of-the-art motion quality, prompt adherence, and visual fidelity—especially for complex action, temporal consistency, and physically convincing interactions (like weight, momentum, and fluid motion) .
On the production side, Runway’s official Gen 4.5 specs list a 720p output at 24fps, with supported durations of 5s, 8s, or 10s . It supports both Text and Image prompt inputs , plus multiple aspect ratios (including 16:9, 9:16, 1:1, 4:3, 3:4, and 21:9) .
Vidofy is built to make Gen 4.5 feel like a practical creative tool—not a research demo. Use Vidofy to iterate quickly (prompt → generate → refine), keep variations organized, and switch between Gen 4.5 and alternative video models (including Veo 3.1) when a project needs a different “look” or control profile.
Precision Motion vs. Platform Flex: Gen 4.5 vs Veo 3.1 on Vidofy
Gen 4.5 and Veo 3.1 are both designed for high-quality generative video, but they differ in output constraints, pricing models, and how their official specs are documented. Here’s a spec-driven comparison using official sources only—plus the shared advantage: both can be accessed inside Vidofy.
| Feature/Spec | Gen 4.5 | Veo 3.1 |
|---|---|---|
| Model category | Video generation model (text-to-video + image-to-video) | Video generation model line (text-to-video + image-to-video) |
| Base prompt inputs | Text, Image | Text prompt, Image prompt |
| Supported clip lengths | 5s / 8s / 10s | 4s / 6s / 8s |
| Frame rate (FPS) | 24fps | 24 FPS |
| Supported aspect ratios | 16:9, 9:16, 1:1, 4:3, 3:4, 21:9 | 16:9, 9:16 |
| Output resolution | 720p | Conflicting official sources |
| Cost model (officially published) | 12 credits per second | $0.20/second (video generation, 720p/1080p pricing tier) |
| Accessibility | Instant on Vidofy | Veo 3.1 Also availabe on Vidofy |
Detailed Analysis
Analysis: Motion realism & prompt adherence
Runway positions Gen 4.5 as a model built to execute complex, sequenced instructions while maintaining motion quality and visual coherence (including physically plausible movement and fluid dynamics) . If your creative brief depends on believable action and clear camera choreography across time, Gen 4.5 is optimized for that kind of direction-first prompting.
Analysis: Choosing the right constraint set (duration, ratios, and workflow)
Veo 3.1’s Vertex AI documentation is explicit about short clip lengths and a smaller set of aspect ratios , while Gen 4.5 offers longer single-clip durations and more output aspect ratios in its published Runway specs . On Vidofy, that translates to a practical advantage: you can prototype the same scene in both engines quickly, then commit to whichever model’s constraints best match the final deliverable.
Verdict: Pick Gen 4.5 When Believable Motion Is Non‑Negotiable
How It Works
Follow these 3 simple steps to get started with our platform.
Step 1: Choose Gen 4.5 in Vidofy
Select Gen 4.5 as your generation model, then decide whether you’re starting from a text prompt or an image prompt. (Gen 4.5 supports Text and Image inputs.)
Step 2: Set your shot constraints (duration + aspect ratio)
Pick a duration (5s, 8s, or 10s) and an aspect ratio (including 16:9 or 9:16, plus additional options like 1:1 and 21:9) , then write your prompt with explicit motion and camera direction.
Step 3: Generate, review, and iterate like a director
Run a first pass, then refine: tighten action timing, clarify camera movement, or simplify multi-action instructions until the sequence reads cleanly. Save your best variations, and (when helpful) compare against Veo 3.1 inside Vidofy before final export.
Frequently Asked Questions
What is Gen 4.5 (and who developed it)?
Gen 4.5 is a video generation model developed by Runway, introduced as “Runway Gen 4.5” on December 1, 2025 .
What inputs does Gen 4.5 support on its official spec sheet?
Runway’s Gen 4.5 specs list base prompt inputs as Text and Image .
What are Gen 4.5’s official output limits (duration, resolution, FPS)?
Gen 4.5 is listed at 720p output and 24fps, with supported durations of 5 seconds, 8 seconds, or 10 seconds .
Which aspect ratios does Gen 4.5 support?
Runway’s Gen 4.5 spec details list multiple aspect ratios, including 16:9, 9:16, 1:1, 4:3, 3:4, and 21:9 .
Does Gen 4.5 generate audio?
Not verified in official sources (latest check).
How does Veo 3.1 compare on official constraints (duration + FPS)?
In Google Cloud’s official Vertex AI model documentation, Veo 3.1 is listed at 24 FPS with video lengths of 4s, 6s, or 8s .